Methodology

Modeling principles

• Assumptions first: key drivers (rates, returns, costs, taxes, timing) are inputs, not hidden defaults.
• Cash flow + balance sheet together: affordability and long-run outcomes are modeled in the same run.
• Opportunity cost is explicit: capital tied up in one choice is capital not compounding elsewhere.
• Mechanics over narrative: the model tracks flows and frictions (fees, taxes, transaction costs) across time.
• Sensitivity over certainty: the primary output is “what changes when assumptions change.”

Scope

Tepuy calculators cover Australian personal finance decisions: property vs shares, buy vs rent, offset account vs shares, mortgage repayments, retirement feasibility, stamp duty, LMI and first-home deposit schemes, plus a set of embeddable single-purpose widgets. Where tax treatment is included, it is implemented as a modeling component rather than advice.

What Tepuy does not attempt

• Forecasting property prices, market returns, inflation, or interest rates.
• Optimizing portfolios or constructing recommended asset allocations.
• Personal advice based on your circumstances, risk tolerance, or goals beyond what the inputs encode.
• Replacing a registered tax agent or licensed adviser on the tax positions described below.

Tax year modelled

The site models the FY2026–27 Australian tax year. The financial year is resolved at run time from the browser’s date rather than hard-coded: July–December resolves to that calendar year, January–June to the year before, so a session in September 2026 resolves to an FY start year of 2026.

The site does not contain an income tax bracket table and does not compute your income tax from your salary. Every calculator that needs a marginal rate takes it as an input — a single flat rate you supply (the Property vs Shares default is 37%, bounded 0–47%). This is a real simplification: it ignores bracket creep, the Medicare levy and offsets. The one exception is the tax on a capital gain in the year of sale: Property vs Shares, Retirement (Australian mode), Offset vs Shares and the CGT Indexation calculator and widget add the gain to your other taxable income that year and tax it through the 2026-27 or 2027-28 resident rates by default, so a large gain is taxed at the brackets it reaches (see the tax rate on a capital gain); each keeps a Flat rate option.

Capital gains tax, and the 1 July 2027 transition

The Treasury Laws Amendment (Tax Reform No. 1) Act 2026 (Act No. 49 of 2026) and the Income Tax Rates Amendment (Tax Reform No. 1) Act 2026 (Act No. 50), both given Royal Assent on 26 June 2026, change how individuals are taxed on capital gains. This is enacted law, not a proposal. From 1 July 2027, for Australian resident individuals, trusts and partnerships, the 50% CGT discount is replaced by cost-base indexation for assets held at least 12 months, with a 30% minimum tax rate applied to the net capital gain after indexation.

What the trigger actually is

This is the single point most commonly misstated, so the calculators are explicit about it: CGT does not turn on the purchase date. It turns on when the gain accrues relative to 1 July 2027. A property bought in 2005 and sold in 2030 is not “grandfathered” for CGT purposes. The separate 12 May 2026 date that appears elsewhere on this site governs negative gearing only — see the next section — and has no bearing on CGT.

What survives the reform

• The 50% discount is kept in full on the part of a gain that accrued before 1 July 2027, whenever the asset was bought and whenever it is sold (an asset held on 30 June 2027 is treated as sold that day and reacquired on 1 July 2027: ITAA 1997 ss 112-155 and 112-160).
• New residential dwellings keep a 50% discount, with a choice of indexation instead (ITAA 1997 s 115-102), where the dwelling meets the Minister’s requirements for a “new residential dwelling”, which the Act leaves to a determination (s 26-160(4)). For a property marked New Build, Property vs Shares takes the lower of the discount and indexation as the taxpayer’s choice: the discount is 50% of the whole gain at the marginal rate (no 1 July 2027 split, no indexation, no 30% minimum, s 119-5(2)); the quarantined-loss pool comes off the gain first and capital works reduce the cost base on both paths. The choice is property only (share lots are never given it). “New Build” on that page is a negative-gearing definition and may not match the Minister’s requirements; no claim is made that any particular dwelling meets them.
• The affordable housing discount of up to 60% is retained in full; the engines cap the election at 60%.
• SMSF, SMSF-pension and company structures are unchanged by the reform and are modelled unchanged (SMSF one-third discount, SMSF pension phase nil, company 30% with no discount).

How a straddling gain is split — a stated modelling choice

A gain that accrues across 1 July 2027 has to be divided between the two regimes. The Act does it with a deemed sale on 30 June 2027 and reacquisition on 1 July 2027 (ITAA 1997 ss 112-155 and 112-160): the gain up to the asset’s value on that date is deferred and keeps the 50% discount at your marginal rate, and that value, indexed from 1 July 2027, is the cost base for the rest (an indexed real gain at the greater of your marginal rate and 30%). The engines do the same, with ONE value for both parts.

Capital works claimed after 1 July 2027 — a stated modelling choice

The deferred gain is the gain on the deemed sale on 30 June 2027 (ITAA 1997 s 112-160(3)(a)(iii)): the 1 July 2027 value less the cost base on that day. Capital works (Division 43) deductions reduce the cost base (s 110-45), so only the part claimed up to 30 June 2027 — pro rata within the year that straddles it — reduces the deferred gain. Capital works deductions claimed after 1 July 2027 are taken off the indexed cost base, unindexed: the cost base for the rest of the gain is the 1 July 2027 value indexed to the sale, less those later claims. Property vs Shares does this; the CGT calculators take a single cost base and no capital works.

Indexation, and why it is indicative

The post-reform slice indexes the cost base by your assumed CPI rate compounded annually over the holding period, then taxes the resulting real gain. Real ATO indexation uses published quarterly CPI index numbers. Annual compounding of a single assumed rate is therefore an approximation of the mechanism, on top of the larger uncertainty that nobody knows what CPI will be over a 20-year hold. Treat the indexed figure as indicative of the shape of the outcome, not as a return-ready number.

Indexation applies only to an asset acquired at least 12 months before it is sold: Property vs Shares tests each share parcel from its own purchase date, so a parcel sold within 12 months of buying it is taxed on its unindexed cost base. Selling costs are part of the cost base: the property’s sale agent fee, and share brokerage on each purchase and each sale, are incidental costs that form part of the cost base, so they reduce the capital gain as well as the cash. A cost of the sale itself is incurred at the sale, so it is never indexed. The sale agent fee is the only selling cost with its own input. Legal, conveyancing and advertising costs on the sale also reduce the taxable gain; include them in the agent fee % if you want them modelled.

The 30% floor

The post-reform slice is taxed at max(your marginal rate, 30%). The floor binds for anyone whose marginal rate is below 30% — a low-income earner realising a large gain pays more under the new rules than their marginal rate alone would suggest.

Age Pension exception (ITAA 1997 s 119-15): the Act does not apply the 30% minimum tax in an income year in which the person receives, at any time, the Age Pension or another listed income-support payment; the indexed gain is then taxed at their ordinary rates. The Retirement planner models this for the Age Pension: in a year the planner pays an Age Pension it taxes the gain through the resident brackets with no top-up (or, in Flat rate mode, the post-1 July 2027 part at the typed rate instead of at least 30%), testing the pension on that year’s balances before the sale. The other payments the Act lists have no input there. Known limitation, documented rather than built: the other calculators (Property vs Shares, Offset vs Shares, Buy vs Rent and the CGT calculator) have no Age Pension model, so the floor is applied unconditionally in them; if you receive the Age Pension or another listed payment, their figures overstate your CGT.

Worked figures, straight from the engine

A $900,000 asset growing at 6.5% for 20 years (sale value $3,171,281, gain $2,271,281), CPI assumed at 2.5%:

• Disposal wholly before 1 July 2027, marginal rate 37% — 50% discount: $420,187
• Disposal wholly after, marginal rate 37% — indexed, floor not binding: $627,715
• Same, marginal rate 20% — the 30% floor binds: $508,958

The third figure is higher than a naive 20%-of-gain calculation precisely because of the floor. It is the case most likely to surprise, which is why it is stated here.

Main residence rules not modelled: the six-year absence rule (ITAA 1997 s 118-145), the six-month overlap when you buy a new home before selling the old one (s 118-140) and the partial exemption (s 118-185). The ATO’s pages are Moving to a new main residence and Treating former home as main residence.

The tax rate on a capital gain: what the law does, and what the calculators do

The law. A net capital gain is part of your taxable income (ITAA 1997 s 102-5), so it is taxed at the progressive resident rates plus the 2% Medicare levy, together with your other income. The part of a gain that accrued before 1 July 2027 keeps the 50% discount and is outside the 30% minimum (ss 112-160(3), 102-6(5), 119-5(2)). The part from 1 July 2027 is indexed (s 110-36(1A)) and then topped up to a 30% rate if the ordinary tax on it falls short (s 119-10), unless you receive the Age Pension or certain other income-support payments in that income year (s 119-15).

The calculators. Property vs Shares, and the pages built on its engine (Beat the ASX, Buy vs Rent and their widgets, and the eight-city article), now do what the law does by default: the property and the shares are taxed as two separate investors, because they are alternative strategies, not one person’s holdings: for each side, that side’s own gains and losses in the sale year are netted (in the Act’s order), the pre-reform slice is discounted and the post-reform slice indexed, and that side’s net capital gain is added to your other taxable income in the sale year and taxed through the resident brackets for that income year (2026-27, or the 2027-28-and-later table with 14% in the first band), plus the Medicare levy on the extra taxable income and the s 119-10 top-up on that side’s post-reform slice. Tax on that side = tax(other income + that side’s net capital gain) − tax(other income). One side’s capital loss never reduces the other side’s tax. Within the shares side, a capital loss on a share sale part-way through the hold offsets that year’s share gains, and a net capital loss left at the end of a year is carried forward to the shares’ later sales, the final sale included (s 102-5(1) Step 2). A holding bought before 1 July 2027 and sold after it is two capital gains or losses in the year of sale: the deemed sale at its 1 July 2027 value (s 112-155(2); a deferred gain, or a deferred loss made in the sale year, s 112-160(3)-(4)) and the real sale measured from that value (indexed for a gain; not indexed for a loss, s 110-55(1)). Each is netted with that side’s other gains and losses, never only with the other half of the same holding. Other income follows the marginal rate you hold at (the first dollar of its bracket: 37% gives $135,001, 47% gives $190,001, 30% or 32% gives $45,001) until you type your own; Beat the ASX assumes 37% and so $135,001, and the Buy vs Rent widget 32% and so $45,001. The brackets stay at their legislated values for every future year (no indexation, so real bracket creep is not modelled), offsets (LITO, SAPTO) and the Age Pension exception are ignored, and every asset is sold in the final year as one lump. Property vs Shares keeps a Flat rate option that applies one typed rate (Medicare included) to the whole gain, as before, and shares it sells before the end are always taxed at the holding-period rate.

Retirement, Offset vs Shares and the CGT Indexation calculator and widget also tax a gain this way by default, through the same tax core and rates: the year’s gains and losses are netted in the Act’s order (a holding bought before 1 July 2027 and sold after it counts as its two gains or losses, as above), the pre-reform slice is discounted and the post-reform slice indexed (only for an asset held at least 12 months, s 114-10), and the net capital gain is taxed on top of your other taxable income in the sale year at that year’s resident rates (2025-26, 2026-27, or 2027-28 and later), plus Medicare and the s 119-10 top-up on the post-reform slice. What each one sells, and when, differs from Property vs Shares:

• Offset vs Shares sells each strategy’s whole share portfolio at the end of the comparison (as PvS does) and nets every parcel in that sale together, one strategy at a time. Purchase brokerage is in each parcel’s cost base and sale brokerage comes off the gain (s 110-25(3), s 110-35(2)). Small sales along the way to pay the fund’s fees keep the typed rate; their capital losses are netted in their income year and any left over is carried forward to later sales, the final sale included (Step 2). Other income follows the shares tax rate (37% gives $135,001); the widget’s 32% gives $45,001.
• The CGT Indexation calculator prices the one sale on the sale date you enter. Other income comes from its Marginal Tax Rate (47% gives $190,001) unless you type one, and its Prior Capital Losses are applied as earlier years’ net capital losses (Step 2). A sale before 1 July 2025 is priced at the 2025-26 rates: earlier years are not modelled. The widget uses $45,001.
• Retirement (Australian mode) sells the non-super balance once, in the year you retire, and each investment property in its own sale year, not everything at the end; every disposal in one income year is netted together. The non-super balance is a holding of units: the starting balance, each contribution, each year’s reinvested income (after its tax) and each amount paid in is a parcel with its own cost and date. At the sale each parcel held on 30 June 2027 is taken to be sold and reacquired at its own value that day (s 112-155), a parcel bought later is indexed from its own date, the 12-month rule applies to each, and money taken out before the sale comes off the oldest parcels first. The Investment Management Fee is treated as an investment fee within the unit price: it lowers the balance’s value and never reduces a parcel’s cost base. In retirement, other income is the income the planner models for you that year (the Age Pension, employment and other assessable income in retirement, and the dividends and interest on your non-super savings; a super income stream from a taxed fund paid at 60 or over is not taxable income, so it is left out); while you are still working it is the bracket your Tax Drag rate implies. There is no top-up in a year you receive the Age Pension or another payment listed in s 119-15; the planner models only the Age Pension, and the other listed payments are not modelled.

Each of these keeps a Flat rate option: one typed rate, Medicare inside it, applied to the netted gain, as the earlier method did, but with the same cost-base rules (brokerage in the cost base, indexation only after 12 months, s 114-10); global mode in Retirement is always flat.

Worked example. A retiree with no other income sells with a $1,500,000 capital gain. Income tax plus Medicare, at 2026-27 (all pre-reform) and 2027-28 (the other two) resident rates, offsets ignored. The 30% minimum tax is computed by the s 119-10 gap method and does not bind in any of the three. Property vs Shares’ progressive default gives exactly these totals with Other taxable income set to $0. The last column is what a flat 37% (the Property vs Shares Flat rate default) would give on the same gain.

Rates: Income Tax Rates Act 1986 (compilation 66), Schedule 7 Part I, and Medicare Levy Act 1986 (compilation 53) s 6, read on 21 October 2026; minimum tax: ITAA 1997 s 119-10(2) as inserted by Act 49 of 2026. The Medicare low-income reduction is not applied (every taxable income here is far above it). The figures are recomputed by a test, not typed in.

Negative gearing

Negative gearing for established residential property purchased after 7:30pm AEST on 12 May 2026 is abolished from the 2027-28 income year (1 July 2027) (ITAA 1997 s 26-155; the Treasury Laws Amendment (Tax Reform No. 1) Act 2026, Schedule 2). Property purchased before that moment is grandfathered indefinitely for this purpose, and a “new residential dwelling” keeps traditional negative gearing.

In the Property vs Shares engine this is implemented as loss quarantining from the 2027-28 income year (1 July 2027): for an established investment property, a net rental loss arising before 1 July 2027 offsets your other income as it always has, and one arising from that date cannot. The year that straddles 1 July 2027 is split by time: the part before it is deductible, the rest is quarantined. The quarantined loss is carried forward, applied against future rental profits as they arise, and at sale against the capital gain, after capital losses (s 102-5(1) Steps 3-4). Whatever is left after that carries forward to the next income year (s 26-155(1)(c)); the model has no other dwelling to use it against, so it has no further effect. None of the quarantined expenditure is in the property’s cost base (s 110-38(8A)). For a new build, losses offset other income immediately, as before. That is the calculator’s assumption: the exemption is for a “new residential dwelling”, which depends on requirements the Minister has not yet determined (s 26-160(4); none on the Federal Register as at 24 October 2026).

Limitation: the calculator has a new-build / established toggle, but no purchase-date input. It therefore models the post-1-July-2027 regime for any established property you enter. If you already own an established property bought before 12 May 2026, you are grandfathered and the calculator’s tax-refund line understates your position — select “new build” to see the un-quarantined treatment, keeping in mind that this also changes the CGT election available to you.

Property acquisition and holding costs

Stamp duty

Duty is computed by a single shared engine covering all eight jurisdictions — NSW, VIC, QLD, WA, SA, TAS, ACT and NT — with separate general, owner-occupier and first-home-buyer schedules where a jurisdiction has them, and a live purpose distinction between owner-occupied and investment purchases. The rate schedules were last checked against the live government calculators on 30 August 2026.

Example: an existing $900,000 NSW investment purchase returns $34,687. Duty schedules change at state budgets; the verification date above is the honest currency of this figure, and it should be re-checked each financial year.

Investment properties in the Retirement Planner

Each property grows at its own rate, its rent grows with inflation, and its loan is serviced from the shared investment loan rate. There is no loan term input: how long a loan runs follows from the balance, the rate and the monthly repayment you enter. A blank repayment is interest-only — the balance never reduces and interest is charged every year until the property is sold. A repayment below the interest causes the balance to grow rather than fall; the planner warns when you enter one.

On sale, the loan is repaid and capital gains tax is deducted through the same CGT engine used everywhere else on this site. The remainder is added to your non-super savings and earns the same after-tax return as the rest of that balance — about 5.0% a year on the default 7% return, 0.85% fees and 30% tax applied to the income portion of the return only. Super contribution tax does not apply to sale proceeds, because they never enter super.

Selling costs are not modelled. No agent commission, legal, or marketing cost is deducted — the proceeds are the sale price less the loan and the CGT, and nothing else. At a typical 2–3% of sale price, a $1.5M sale would really cost $30,000–$45,000 more than the plan shows. If a sale price would not cover the loan and the tax, the planner reports $0 proceeds rather than a residual debt, and warns that your real position is worse by the difference.

Negative non-super balances are held at zero. Where interest exceeds rent by enough to push non-super savings below zero, the planner floors them rather than carrying a debt forward. This is deliberate: the model has no borrowing facility, so a carried negative would compound at the portfolio return rather than at a real borrowing rate — wrong in a different and less visible way. The effect is that a strongly negative-geared plan is shown slightly better than it would really be.

Lenders Mortgage Insurance

LMI is estimated from a nine-band LVR table (80–82% through 95–97%), with three loan-size brackets within each band (up to $300k, up to $600k, above $600k), a ~15% loading for investment purposes, and stamp duty on the premium added at a default 10%. No LMI is charged at or below 80% LVR; above 97% the tool declines to quote rather than guess, and loans above $3M are referred out.

Example: a $600,000 loan at 85% LVR returns $6,534 at a 0.99% base rate. Limitation: LMI premiums are set by individual insurers and lenders and are commercially variable. This repository carries no dated source for the premium table, unlike the duty schedules. Treat LMI as an order-of-magnitude estimate and get a real quote before committing.

Land tax

Annual land tax on an investment property is modelled for all eight jurisdictions from each one's 2026-27 scale for an individual owner (general rates: no trust, company, absentee-owner or foreign-owner surcharge), charged on the land share of the property's value as it grows. A principal place of residence pays none. The scales are one data file that both engines read, taken from Revenue NSW (thresholds and rates, last updated 16 March 2026), the State Revenue Office Victoria (current rates, updated 29 September 2026), the Queensland Revenue Office (individuals, last updated 23 July 2024), the WA Department of Finance (land tax assessment, last updated 20 May 2026), the State Revenue Office Tasmania (rates from 1 July 2025, last published 2 September 2026), all read on 24 October 2026. South Australia's figures are the owner's browser reading of RevenueSA's 2026-27 rates and thresholds, dated 24 October 2026, and the ACT's come from the instrument itself, the Taxation Administration (Amounts Payable—Land Tax) Determination 2026 (DI2026-152, from 1 July 2026), read on 24 October 2026. The Northern Territory has no land tax.

Valuation date. Land tax for each year uses the land value at the start of that year, the valuation the tax is based on (in every state). Averaging. NSW charges on the 3-year average of the land value, and the ACT on the 5-year average unimproved value; the model averages the yearly valuations the same way, ending at that start-of-year value and valuing the years before purchase at the purchase value deflated by the growth rate. The ACT adds its fixed charge of $1,778. WA includes the Perth metropolitan region improvement tax (0.14% of the value above $300,000), which does not apply outside the Perth metropolitan region.

Later years. NSW's thresholds are frozen, and Victoria's rates are set for the 2024-2033 land tax years, so both are held as they are (Victoria's after 2033 too, since no later scale is published). South Australia's thresholds are indexed each year by the average change in site values and stay unchanged when that change is negative; the model uses its own land growth rate as the proxy for that average, with the threshold indexed to the same valuation date as the land value. Queensland, WA, Tasmania and the ACT publish no rule for later years, so their 2026-27 scales are held in nominal dollars.

Depreciation

Division 43 capital works is claimed at 2.5% of construction cost per year for the remaining eligible period; Division 40 plant and equipment is depreciated on a diminishing-value schedule per item. Both feed the taxable-income line, and therefore the negative gearing pool above.

Brisbane council and water suggestions in Property vs Shares

With State set to Queensland, Property vs Shares shows a Brisbane 2026-27 suggestion under Council Rates and Water Rates, each with an Apply button; nothing changes until you click it, and the applied figure is then treated as your own. Council: the rating category comes from Purpose and Property Type (an investor’s house is category 7, an investor’s apartment or a townhouse with strata levies category 14, an owner-occupier’s house category 1 and apartment category 10; an inner-city unit size band is used only if you choose one). The general rate, the Environmental Management and Compliance Levy and the Bushland Preservation Levy are each the larger of the cents-in-the-dollar rate times your average rateable value and that charge’s minimum, plus one waste utility charge of $576.08. Without a rateable value the suggestion is the minimum charge, a floor: $2,150.56 for category 7, $2,187.24 for category 14, $1,620.00 for category 1 and $1,827.44 for category 10. Apply puts the minimums and the waste charge in the Base Charge, which rises with Inflation (CPI), and anything above the minimums in the Rate per $1k Land, sized so that today’s land value reproduces it; that part then follows the land value. A unit’s rateable value is a share of the scheme’s value, and the parity factor (clause 4.1) is not modelled. Water: the water and sewerage service charges, $0.597 and $2.107 a day, come to $986.96 a year and are always the owner’s. An owner-occupier also pays usage at the tier 1 price plus the state bulk water charge, $4.565 per kL up to 300 kL a year and $5.694 above it, so the Urban Utilities guide’s worked example of 27 kL a quarter (108 kL a year) gives $1,479.98. An investor’s suggestion is the service charges only: under the Residential Tenancies Authority’s rules a tenant pays water usage only if the home is individually metered, water efficient and the lease says so. Sewerage usage is not modelled, because residential customers are not charged it. Sources, read 22 October 2026: Urban Utilities Pricing Guide 2026-27, Brisbane City Council Resolution of Rates and Charges 2026-27 and RTA water charging.

Australian Government 5% Deposit Scheme

The Australian Government 5% Deposit Scheme was formerly known as the Home Guarantee Scheme. It is open to first home buyers and to anyone who has not owned a property or land in Australia in the last 10 years. From 1 October 2025 income tests were removed entirely, the 35,000-place annual cap was removed, the Regional First Home Buyer Guarantee was merged into it, and price caps were raised. Property price caps in the engine, verified against firsthomebuyers.gov.au on 1 September 2026:

• NSW $1,500,000 capital · $800,000 other
• VIC $950,000 · $650,000
• QLD $1,000,000 · $700,000
• WA $850,000 · $600,000
• SA $900,000 · $500,000
• TAS $700,000 · $550,000
• ACT $1,000,000 (single tier) · NT $750,000 · $600,000

The higher tier covers capital cities and designated regional centres. The cap that actually applies to you is set by postcode, and suburbs can span postcodes in different tiers — so a figure here is indicative and must be confirmed against the official price cap tool before you rely on it. The single-parent pathway (2% deposit, single parents and legal guardians) is part of this same scheme and reads the same cap table — it was the separate Family Home Guarantee until 1 October 2025. It carries no income test, no place cap and no waitlist. What differs is the deposit (2% rather than 5%, with the government guaranteeing up to 18% of the property value) and the eligibility test: you must be single, be the parent or legal guardian of one or more dependent children, and apply alone. Unlike the 5% pathway, it does not require you to be a first home buyer or to have gone 10 years without owning property — prior ownership in the past 10 years is permitted provided no other property interest remains once the new home settles.

Superannuation

• Concessional contributions cap: $32,500 for FY2026–27 (resolved by financial year, not hard-coded — earlier years are carried in the same table: $30,000 for FY2024–25 and FY2025–26, $27,500 for FY2021–22 to FY2023–24).
• Non-concessional contributions cap: $130,000 for FY2026–27.
• Transfer balance cap: $2,100,000 for FY2026–27 (ATO-indexed 1 July 2026).
• Superannuation Guarantee rate: 12%.
• Contributions tax: 15% on concessional contributions; 15% on accumulation-phase earnings; nil in pension phase.
• Pre-60 withdrawals: modelled through a single effective rate you supply (default 17%), rather than by decomposing your balance into taxable and tax-free components.

Caps are indexed and change. These are the figures the engines currently carry; check them against the ATO at the start of each financial year.

Monte Carlo simulation

The Retirement Planner runs 1,000 simulated paths. Annual returns are drawn from a lognormal distribution calibrated so that the median simulated path equals the return you entered — because a return quoted as “8% p.a.” is a compound annual growth rate, not an arithmetic mean. The arithmetic mean of the distribution therefore sits slightly above your input, by roughly σ²/2, which is correct.

Volatility is taken from the portfolio preset you choose: cash 1.5%, conservative 6%, balanced 10%, growth 13%, high growth 16%, and 12% for Custom. Inflation is simulated as a correlated series with its own volatility (0.5% for cash rising to 1.4% for high growth, and 1.0% for Custom), rather than held fixed. A partner, when enabled, is simulated stochastically alongside you — sharing the same annual market draw, but with their own balances, contributions and retirement age. An adaptive withdrawal rule reduces the draw by 10% when the portfolio falls more than 20% below plan.

How the success probability is banded

The proportion of paths that do not run out of money is reported against four bands. These are the engine’s own thresholds, and every surface on the site uses them:

• Strong — 85% and above
• Moderate — 70% to below 85%
• At risk — 55% to below 70%
• High risk — below 55%

A probability is a property of the assumptions you entered, not a measurement of your future. Moving your assumed return by one percentage point will move this number more than most people expect — which is the argument for reading it as a sensitivity, not a score.

The Offset vs Shares calculator also offers a Monte Carlo view; it runs 300 paths, not 1,000.

Cash-flow modeling

The core unit of analysis is a time-series of cash flows. Depending on the calculator, this may include contributions, repayments, rent, dividends, expenses, and tax impacts. The model then tracks how cash flows affect:

• Net cash position: the cumulative cash burden or surplus over time.
• Asset values: property value, share portfolio value, and associated equity.
• Liquidity constraints: whether a scenario remains feasible under the chosen assumptions.

Share parcels are tracked on a FIFO ledger, so a partial sale disposes of the oldest parcels first and each parcel carries its own holding period into the CGT calculation. Dividends are grossed up for franking credits at the 30% corporate rate and the excess credit is refunded or applied according to the structure you selected.

Timing conventions

Tepuy uses consistent timing rules (e.g., year 0 vs year 1 treatment). Where relevant, the calculators avoid “free money” artifacts such as charging interest or earning rent in periods where the model states those cash flows should not yet apply.

Off-the-plan purchases in Property vs Shares

Property vs Shares has an optional off-the-plan setting for a contract signed now and settled months or years later. With it on, the comparison runs to a fixed end date. The deposit is paid at signing; the balance of equity, stamp duty and costs come from where you say: saved from income in equal monthly amounts during the wait (the default), arriving at settlement (a gift, sale proceeds or another loan), or already set aside at signing (the model every earlier link and saved scenario used). In all three, both sides receive the same cash on the same dates; the shares side invests each amount as it arrives, while the property side holds it in cash, taxed, until settlement (or holds none, if it arrives then). Until settlement the property earns nothing and pays no loan or holding costs, while its value moves with the growth rate you set for the wait. For capital gains tax the asset is acquired when the contract is entered into, not at settlement (Income Tax Assessment Act 1997 s 109-5), so the hold period, the cost base and the 1 July 2027 value run from the contract date. The main residence exemption is the exception: it runs over the ownership period, which starts at settlement (s 118-130(2); the ATO: “If you buy your home, the ‘time you acquire it’ is the settlement date of the contract”, ATO: Moving to a new main residence), so a home lived in from settlement is fully exempt. With the setting on, stamp duty is worked out as for a new home (an off-the-plan purchase is a contract to buy a home on a proposed lot), and by default is paid with the transfer at settlement. For Queensland you can instead pay it in month 2 after signing, the month-end at or before the 74 days Queensland’s Revenue Office gives for an unconditional contract lodged as a relevant transfer agreement (60 days to lodge, 14 to pay); a contract conditional on plan registration can ask for more time to lodge, and which timing applies depends on the contract and the lodgement route. For an ELN transfer lodgement QRO gives 30 days to lodge and 14 to pay (about 44 days); this calculator models the relevant-transfer-agreement route (74 days, rounded to month 2); the lodgement route depends on the contract, so check with the conveyancer. NSW investors cannot defer the duty on an off-the-plan purchase; every other state is a generic assumption, not yet sourced. The deposit is assumed to earn no interest for you (it sits with the developer or in a trust). If your contract pays you the interest, this calculator does not include it. With the setting off, nothing changes. The full list of what it models, and what it leaves out, is in how the settlement period is modelled on the calculator page.

Opportunity cost and comparability

Many comparisons are biased because they unintentionally give one option “extra capital” or “extra cash flow.” Tepuy aims to compare options under the same economic constraints by making these quantities explicit:

• Upfront cash: deposit, stamp duty, legal fees, and other acquisition frictions.
• Ongoing cash burden: net costs after rent/income, maintenance, fees, and tax effects.
• Alternative investment return: what the forgone capital could earn elsewhere.

Known limitations

These are the places where a calculator on this site will give you an answer that is narrower, or less current, than it might appear. They are listed because knowing the edge of a model is part of using it.

• Beat the ASX uses one national rental yield. Rent is estimated as a flat 3.5% gross yield of the purchase price everywhere in Australia. Because every other term in that comparison also scales with price, the price nearly cancels out and the breakeven growth rate is almost the same at every price — about 4.22% at the shipped defaults: 4.23% for a $400,000 home and 4.21% for a $3,200,000 one, the small difference coming only from the tax brackets on the share gain (a bigger gain pays a higher average rate). The tool cannot tell you that one city clears the bar more easily than another, and it is not a suburb ranking. Choosing your suburb changes the dollar figures, not the percentage.
• Interim share-sale CGT is paid from the sale proceeds in the year of sale. Where Property vs Shares sells shares part-way through the hold (to cover the fund’s fee or margin interest, or to match the property side’s cash flow), it sizes the sale so you receive the cash you need after brokerage and the CGT on that sale, and the tax is paid from the proceeds that year. This is a simplification: real payment follows the tax return. Beat the ASX and the other tools that run the same engine inherit it.
• An offset account balance comes back at exit. In Property vs Shares the whole offset balance, the starting balance and every yearly contribution, is part of the property side’s net proceeds at the end (and in each year’s “if sold” figure), and in both neutrality modes the whole balance reduces the loan interest. The starting balance is in both sides’ starting capital, so the shares side holds the same money in its portfolio. In pocket-neutral mode (the default) each yearly contribution is charged to the property side’s cash flow and mirrored into shares. In consumption-neutral mode (the forced-savings view) the contributions, like loan principal, are the owner’s saving: charged to neither side’s cash flow, not mirrored, and kept by the property, so that view is not like-for-like and favours property by design.
• Beat the ASX applies a fixed 37% marginal rate. Its breakeven is solved against the Property vs Shares engine, so capital gains tax and the 1 July 2027 reform are applied on the share side — but the page has no tax control, so the rate is fixed at 37% and cannot be varied. Until this was wired up the page charged no tax at all and the rate it published was 1.17–1.59 percentage points too high in every scenario measured. Use the full calculator to set your own rate.
• The buy vs rent pages hold rent flat in real terms. Rent grows at a fixed 3% a year, and the comparison assumes an owner-occupier in NSW paying stamp duty, council rates, water, insurance at 0.3% of value and maintenance at 1% of value. The council base charge ($1,800) and water ($800) are entered in today’s dollars and rise with inflation at 2.5% a year (the RBA’s target midpoint, which ASIC also uses for super forecasts); the land part of council rates, insurance and maintenance follow the property’s value. The share side is the slider's total return — dividends and franking credits are not modelled separately, which is conservative toward shares.
• Property vs Shares escalates some owning costs with one inflation input. The Inflation (CPI) input (default 2.5%, the midpoint of the RBA’s inflation target, which ASIC also uses for super forecasts) raises strata levies (which can take their own rate), water and the council base charge every year from the contract date, and indexes the CGT cost base. The land part of council rates, insurance and maintenance follow the property’s value, and agent fees follow rent. For a New Build, maintenance can ramp from 0.2% of value in the first year to 0.8% over 20 years; those three figures are our assumptions, not figures from an Australian source, and for an apartment strata levies already cover the building. Real strata, council and water charges are set by the body corporate, council and water authority and can rise faster or slower than CPI. In the Monte Carlo run the same cost lines move around the CPI path in place of the fixed escalation, not on top of it. Beat the ASX and the eight-city comparison carry no council, water or strata cost, so this does not change them.
• Property vs Shares has two margin loan modes. Either way the loan is sized once, at the start, as starting capital × LVR ÷ (1 − LVR), where LVR is the loan divided by the share portfolio. In Fixed dollar loan mode (the default) the loan then stays at that dollar amount, so the LVR falls as the portfolio grows. In Hold LVR at the target mode the loan is reset at every year-end, after the shares are valued, to the target LVR × the whole portfolio: extra is borrowed and invested (with brokerage), or shares are sold to repay it (brokerage and CGT paid from the proceeds). It is not done in the final year. Interest is deductible at the marginal rate and is paid from dividends first, then by selling shares. In the Monte Carlo, a year-end LVR above the lender’s maximum is counted as a margin call and the share of paths with one is reported. The maximum (default 75%) is our assumption within the 40–80% range the RBA reports for standard margin loans, and the RBA puts the buffer before a call at typically 5–10% (Reserve Bank of Australia, Recent Developments in Margin Lending in Australia, Bulletin, December 2009, retrieved 21 October 2026). A lender’s own product disclosure statement was not available to us, so no lender’s figure is used. There are no lender-specific rules, no buffer beyond the maximum, no security-by-security LVRs and no fees, and the margin rate (default 7.5%, an assumption) is constant. Re-gearing compounds leverage hard and the same inputs can move the result by millions.
• Beat the ASX suburb medians carry no capture date. The 624 suburb medians are indicative approximations for 2026. There is no dated source for them in this repository, so the page states them as approximate rather than attaching a precision it cannot support.
• Offset vs Shares models the 1 July 2027 CGT reform (2026-09; previously it applied a flat 50% discount regardless of when the gain accrued, understating post-2027 CGT by roughly 37% on a 5-year hold, 47% on 10 years and 68% on 25 — disclosed at the time via a banner on the calculator). Each FIFO share parcel is now split at its own estimated 1 July 2027 value: the 50% discount up to that value, CPI-indexed cost base at a 30% minimum tax after (33.33% inside super, unconditionally, unaffected by the reform). CPI uses a constant assumed rate, not the ATO’s published quarterly figures, and the 1 July 2027 value of the Subdivision 112-E deemed sale is an estimate, not a market valuation — same two caveats Property vs Shares already carries for the same reason.
• No income tax engine for salary. Marginal rates are inputs, not computed, except the tax on a capital gain in the sale year, which Property vs Shares, Retirement (Australian mode), Offset vs Shares and the CGT Indexation calculator and widget compute through the resident brackets by default (see the tax rate on a capital gain). See “Tax year modelled” above.
• No HECS/HELP engine. Where this site discusses student loan repayments it does so in prose only; no calculator models compulsory repayments or indexation.
• No Age Pension modelling outside the Retirement planner, which is why the CGT 30% floor cannot be waived for income-support recipients in the other calculators as the Act allows (the Retirement planner waives it in a year it pays an Age Pension).
• No purchase-date input for negative gearing grandfathering. See that section above.
• Nothing here is forecast. Growth rates, returns, inflation and interest rates are all assumptions you supply. The calculators do not predict them and do not have a house view on them.

Sensitivity and interpretation

Tepuy outputs should be read primarily as sensitivity analysis: they show which inputs dominate outcomes. In many scenarios, a small number of parameters drive most of the spread (e.g., interest rates, rent yield, growth rates, time horizon).

Recommended usage

• Run a base case with conservative inputs you are willing to defend.
• Run stress cases (rates higher, vacancy higher, costs higher, returns lower).
• Look for break-even regions rather than a single “winner.”

Definitions (common outputs)

• Equity: asset value minus liabilities (where modeled).
• Net cash position: cumulative cash outlay/surplus over time.
• NPV: present value of a scenario under a chosen discount rate (where included).
• IRR: discount rate that makes NPV equal to zero (where included). In Property vs Shares the upfront outlay is year 0, each year's flow falls at the end of that year, and the sale proceeds fall at the end of the final year.

If a specific calculator implements a definition differently, that calculator should be treated as the source of truth for that context.

Disambiguation

Tepuy Solutions is not affiliated with thetepuy.com or other non-financial brands using the name “Tepuy”.

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