The engine at full depth

The calculator on this website is a browser-based version of the engine that this financial advice practice has been using in its own work for some time now. The calculator does not retrieve its own market data. The website transmits the data files to the calculator, the calculator performs the calculations, and the page displays the result. This page sets out what data the calculator contains, what fees it charges and how it applies tax. It also explains how the calculator selects its time periods and how many checks are involved.

The seven asset classes used in this calculator
The data series
The fee layers
Super accumulation
Pension accounts
Accounts outside super
Franking and the income split
The two capital gains regimes
Today's dollars
The window rules
Term deposits
The checks behind the numbers
The limits of the engine

The seven asset classes used in this calculator

Class	In the code	Income assumption for the tax split	Fund fee the site applies
Australian sharesgrowth	AusEq	4.0% a year of the balance, 77% of it franked at a 30% company rate from FY1988	0.053%mean of VAS 0.07, A200 0.04, IOZ 0.05
International sharesgrowth	IntEq	2.5% a year, unfranked	0.117%mean of VGS 0.18, BGBL 0.08, IWLD 0.09
US sharesgrowth, optional	USEq	1.5% a year, unfranked	0.035%mean of VTS 0.03, IVV 0.04
Australian listed propertygrowth, optional	AusProp	5.0% a year, split five ways for tax. See "The A-REIT distribution" below	0.230%VAP 0.23
Australian bondsdefensive	AusFI	the financial year's average 10 year government bond yield, from its own series, plus the credit premium. See "The credit premium on the bond component" below	0.130%mean of VAF 0.10, IAF 0.10, OZBD 0.19
Cashdefensive	Cash	the whole return is income, unfranked	0.125%mean of AAA 0.18, BILL 0.07
Term depositsdefensive	TermDep	the whole return is income, unfranked	none. A term deposit is money with a bank, not a fund, so there is no management cost to subtract and the flat fee override doesn't reach it

Fund names appear here as the basis of a fee assumption, not as recommendations.

The splits inside the mix

A lower limit applies to cash, which is set as a percentage of the total portfolio: 3% in super accumulation and outside super, and 8% in a pension account. This lower limit restricts the growth portion to the remaining balance.
What remains after the growth allocation and the cash lower limit is the defensive block. This is divided into three parts. Bonds and fixed-term deposits each receive the proportion specified by the user. Cash takes up the remaining amount in addition to its lower limit. Bonds hold the entire remaining amount, unless the user makes any changes.
By default, the growth block is split 45% into Australian shares and 55% into international shares, although the user can adjust this allocation.
The engine maintains a constant weighting, meaning that the portfolio is rebalanced once per financial year as a matter of design. The engine includes no buying or selling costs and no capital gains from this rebalancing.

The data series

There are currently 23 data series in use. The engine reads 21 of these, while the other two provide figures mentioned elsewhere in this section without any calculations being carried out. The full list is on the data and licences page. Each entry there contains the conditions set by the publisher, as well as the source reference that the series must include.

Series the engine reads

Series	Publisher	What the engine does with it
Asset class total returns, as published	Vanguard Investments Australia	the financial year returns for shares and property, in data/fy_returns_full.csv, 56 financial years from FY1971 to FY2026
Asset class total returns, the underlying compilation	Andex Charts Pty Ltd	the same numbers, one step upstream. Recorded separately because the compilation and the publication carry different terms
S&P/ASX accumulation indices and the S&P 500	S&P Dow Jones Indices LLC	the indices underneath the Australian and US share returns
MSCI World ex-Australia	MSCI Inc.	the index underneath the international share returns
Bloomberg AusBond Composite and Bank Bill indices	Bloomberg Index Services Limited	the indices underneath the incumbent bond and cash returns. This practice has built free substitutes for both from Reserve Bank data, so this dependency can be dropped
124 year Australian share return table	Fintech Equity Pty Ltd	the Australian share years before FY1971, in data/fy_returns_extended.csv, FY1951 onward. The same file carries the bond and cash years of that era, and the rebuilt Reserve Bank series are built to take those over
Australian government bond yields, table F2	Reserve Bank of Australia	the 10 year yield that sets the bond income assumption, in data/bond_yield_fy.csv. It is also the input to the rebuilt bond return series
Historical interest rates and bond yields	Reserve Bank of Australia, Occasional Paper 8	the bond yields before FY1970, in data/bond_yield_fy_extended.csv
Term deposit and retail deposit rates, table F4	Reserve Bank of Australia	the published one year term deposit rate, which is what the term deposit series is built from
Term deposit rates, rolling one year	In Your Interest Financial Planning, computed from Reserve Bank data	the term deposit return for each financial year, in data/term_deposit_rates_fy.csv, FY1983 to FY2026
Consumer price index	Australian Bureau of Statistics, through Reserve Bank table G1	the actual inflation rate for each financial year, in data/cpi_fy.csv, FY1923 onward. This is the one series that reaches every figure on the site
Lifestage glide paths	Australian Prudential Regulation Authority, Quarterly MySuper Statistics, Table 1b	the growth share by age of the published MySuper lifecycle products, reduced to five anonymous percentile curves in data/lifestage_glide_paths.json, read only when a visitor ticks the lifestage strategy on tool 8
Dwelling prices	OECD analytical house price indicators, Australia, from ABS sources	the nominal house price index averaged over each financial year, FY1971 to FY2025, in data/dwelling_price_fy.csv, the home's value path in rent or buy
Rents	Australian Bureau of Statistics, Consumer Price Index, Rents expenditure class, weighted average of eight capital cities	the rent index averaged over each financial year, FY1973 to FY2025, in data/rent_index_fy.csv, the rent path in rent or buy
Earnings by qualification	Australian Bureau of Statistics, Employee Earnings, August 2025	the level of the career-paths tab's wage profiles (a bachelor degree about 1.70 times, a certificate about 1.40 times no post-school qualification), in data/earnings_paths.json
Income by age	Australian Bureau of Statistics, Personal Income in Australia, 2022-23	the shape by age of the same wage profiles; the cross of the two is a construction the assumptions page names
Housing loan rate	Reserve Bank of Australia, Statistical Table F5, series FILRHLBVS	the banks' standard variable owner-occupier rate averaged over each financial year, in data/housing_rate_fy.csv, the loan rate of tool 8's SMSF property scenario plus its margin
Housing rates actually paid	Reserve Bank of Australia, Statistical Table F6, from APRA's Economic and Financial Statistics	the owner-occupier variable rate on outstanding loans from July 2019, the source of the discount schedule's recent years in data/mortgage_discount_fy.csv, which the mortgage decision reads
Wage growth by financial year	Australian Bureau of Statistics (Average Weekly Earnings, 6302.0), with the years before FY1983 from the ABS data the Reserve Bank compiled in Occasional Paper 8	each financial year's growth in average weekly ordinary time earnings, in data/awote_fy.csv, FY1971 onward, read for every stretch to index the concessional cap, and to grow the yearly amount when the contribution growth is "Wage growth (AWOTE)", the default in every account type since 10 October 2026; the method and the splice are in data/AWOTE_SERIES.md
Tax rules, rates and thresholds	Australian Taxation Office	the rates, caps, and thresholds in the tax section that follows
Legislation	Office of Parliamentary Counsel, Federal Register of Legislation	the primary text behind the same rules, and the pension minimum drawdown factors

Series quoted but not used in calculations

The numbers of these two series are not used in any calculation on this site at the moment. Their conclusions appear in explanatory pages and they are listed here for completeness.

Series	Publisher	Where it appears
SPIVA Australia Scorecard figures	S&P Dow Jones Indices LLC	the share of active funds that trailed their index, on the active and passive page. That page is reached from the professionals section and is deliberately not linked from here: the scorecard is published for institutions only
Australia Persistence Scorecard figures	S&P Dow Jones Indices LLC	how rarely a top quarter fund stayed there, on the same page

The fee layers

The calculator engine includes four types of costs. Tax treatments differ depending on the type of account (investment, super, pension). It charges every layer on the average of the opening balance and the pre-fee closing balance.

Layer	Default	How the tax treats it
Fund fee, per class	the per-class figures in the preceding class table	no credit and no deduction inside super, either kind of super. Deductible at the marginal rate outside super. Subtracted from the gross index return, because the return series is before fees. The fee lowers the fund's taxable earnings, so a super fund's 15% tax falls by about 15% of the fee; the engine gives no such benefit in super accumulation, a difference of about 0.03% a year on a 0.2% fund fee
Advice cost	1.0% a year before goods and services tax (GST), so 1.1% with it; selectable at 0.9, 1.0, 1.1, or 1.2, or turned off	advice costs receive a tax credit of 15% as they count as an expense to the superannuation fund. No credit in a pension. Outside super this tool allows no deduction for advice, because only the part of the advice cost that relates to tax advice is deductible, and most advisers do not state any part of their fee as tax-deductible
Platform fee	0.25% a year before GST, so 0.275% with it	15% credit in super accumulation, no credit in a pension, deductible at the marginal rate outside super
Fixed amount in dollars	none by default	held in start-year dollars and indexed along the same inflation path as everything else in the window. Super accounts only: it gets the 15% credit in accumulation, none in a pension, and outside super it is not charged at all

The engine applies 10% GST to the advice cost and the platform fee, and to nothing else. The code holds that as a factor of 1.10.

Super accumulation

Investment income is taxed at 15% on the grossed-up amount, which includes the franking credits. The credits are then subtracted from the tax as an offset. Where the net tax is positive, it is then reduced by a credit worth 15% of that tax, which brings the effective rate to 12.75%. Where franking credits exceed the tax, the excess passes through as a refund.
The contribution is treated as a before-tax (concessional) contribution and is taxed 15% on the way in.
It is capped at $32,500 a year in start-year dollars, indexed along the window's own inflation path. If the contributions entered are above the yearly cap, the calculator uses the cap instead.
Division 293, the extra 15% for high earners, is optional. With it on and no income entered, the whole 30% applies to every concessional contribution. With a taxable income entered, the extra 15% applies only to the part of the contribution that, added to that income, passes the $250,000 threshold. The threshold is fixed by default, and the user can set it to rise with inflation or at a chosen rate.

Pension accounts

A pension account pays no tax on investment income, and franking credits are refunded in full.
Statutory minimum drawdowns are paid out and counted in the result. They are paid at the age-based rate on the opening balance, mid-year on average: 4% under 65, 5% at 65 to 74, 6% at 75 to 79, 7% at 80 to 84, 9% at 85 to 89, 11% at 90 to 94, and 14% from 95.
The engine adds no contributions in a pension account.

Accounts outside super

The marginal rate selected applies to the grossed-up income, which includes the franking credits. The credits are then subtracted from the tax as an offset.
The rate that applies at a sale is set separately from the ongoing rate, because the year of a sale is often not a typical year.
The engine charges no fixed dollar costs outside super.

Franking and the income split

Each class has an assumed cash income yield. That yield sets the part of the return that is taxed each year. Of the Australian share income, 77% is treated as franked at a company rate of 30%. That applies from FY1988 onward, the first full year of imputation. Before that year the credit is zero.

The A-REIT distribution

Australian listed property has multiple income streams. An A-REIT is a trust, and a trust pays no company tax and therefore has few, if any, franking credits. The engine splits the distribution five ways rather than taxing all of it at the marginal rate.

Component	Share	How the engine taxes it
Ordinary incomenet rent, interest, unfranked dividends	44.3%	assessable in full
Capital gains distributed	46.7%	assessable at half outside super and two thirds inside it, which is the CGT discount each account type receives
Franked dividends	4.3%	assessable in full, and it carries the credits below
Foreign income	4.3%	assessable in full. The foreign income tax offset the notices report is not modelled
Not assessable	0.4%	not taxed, and not deducted from the cost base either. See the note on tax-deferred amounts below
Franking creditsattributed on top of the cash	2.25%	of the cash distribution, from FY1988 like every other credit here. These credits come on top of the cash and are not one of the five shares. Normally a credit is 30/70 of the franked dividend it comes with. The credits in Vanguard's notices are higher than that rule gives, so the engine uses the reported figure.

The above five income streams are cash-weighted over the nine financial years FY2018 to FY2026. They come from Vanguard's own 36 available quarterly distribution tax estimate notices for its Australian Property Securities Index ETF. The year-to-year variation is wide. The capital gains share alone ran from 6.5% to 73.2% over those nine years. Therefore the percentage split assumed is an average of multiple years.

More details:

Distributed capital gains are taxed in the year they arrive. They are gains the trust realised and paid out, so they are assessable on receipt.
The annual treatment follows current law, not the 2027 rules. Under the 2027 rules the discount is abolished, so the same distributed gain would be assessable in full. The engine applies the current law's discount to the annual figure. The reason is that the annual income tax feeds the balance, and the two disposal regimes are computed off that one balance. A balance that depended on the regime would leave the two capital gains figures in the next section measuring two different portfolios. They would no longer measure one portfolio under two exit taxes.
Tax-deferred amounts are treated as zero. A tax-deferred distribution is not assessable on receipt and reduces the cost base of the units instead. The engine ignores such adjustments. Vanguard reported tax-deferred as exactly zero in all twenty quarters for which it reports this amount. The whole non-assessable component is 0.4% of the total.

The default growth block does not include any A-REIT weighting. This split therefore only affects a result if the user puts together a growth mix that includes listed property.

The credit premium on the bond component

The bond series consists of government bonds. The index it tracks, the standard Australian bond index, consists of 90.6% government and quasi-government bonds and approximately 9% corporate bonds. This corporate component provides an additional return. The engine adds it as a value that can be set by the user, rather than integrating it into the series.

The default value is 0.1% per annum and is APPLIED BY DEFAULT, meaning that any portfolio containing bonds will have this value unless the user disables it. The range is between 0 and 1.0% per annum, and if set to zero, the bond component is government bonds only.
Three independent metrics quantify the credit component of this index at approximately 0.1 percentage points per annum. The first is the realised fund return compared with a pure government bond fund, with the difference in duration factored out. The second is the forward yields to maturity, with the same adjustment applied. The third is the Reserve Bank's spread calculation, applied to the index's corporate bond weighting. Around 0.5% corresponds to a deliberately corporate-oriented portfolio, such as a credit fund.
The premium is added to the bond weighting's share of the annual return. It is also added to the bond yields, on the basis of which the tax allocation is made, as the extra yield is taxable. A premium that increases the return without increasing the tax burden would result in an overstatement of the after-tax result.
It is added uniformly each year, which is right on average but wrong in its pattern over time. Real credit spreads widen when markets are under pressure. In FY2022, the worst year for Australian bonds in the record, corporate bonds lost more value than government bonds, taking into account their shorter maturities. The text beside the control in the calculator says so too.
For this reason, the premium is deliberately OMITTED from the monthly identification of price declines in the stress test. A constant inclusion would make a decline appear less severe in the very year in which the facts show that credit conditions have exacerbated it. Consequently, the identification of price declines and the resulting return for the year of sale continue to be based on the market's own monthly figures. The held run either side of that comparison does carry the premium, because it is an annual figure.

The two capital gains regimes

The calculation engine does not model capital gains tax for shares on a year-by-year basis, as an index fund distributes almost no realised gains. Australian listed property forms the exception here. Its gains are treated as income in the section above and not here, as they are distributed rather than realised on a sale.

This section deals with capital gains tax at disposal, for accounts outside super only. The calculation engine calculates this twice: once under current law and once under the 2027 rules. Both calculations use the same cost-base layers, one per financial year. Each layer consists of that year's contribution plus the net income reinvested in it.

	Current law	2027 rules
The gain	sale value less the cost base as it stands	sale value less a cost base with every layer indexed by inflation from its own financial year to the sale
The discount	50% on every layer held more than twelve months. The final year's addition is under twelve months old and is taxed undiscounted	none
The rate	the rate at sale selected	the rate at sale, or 30%, whichever is higher. The minimum applies at every marginal rate
A loss	no tax, and no refund implied	no tax. Indexation cannot create a loss or make one bigger

The model applies these same two tax regimes to a panic sell-off in the middle of a time window, specifically in the view that shows what a complete sell-off would cost. The comparison between selling and holding therefore includes the tax on the sale.

Today's dollars

Inflation is factored into the model at exactly one point. A running deflator starts at 1.0. At the end of each financial year, the model multiplies this value by one plus that year's inflation rate. If an inflation rate is selected, the model uses that. Otherwise, the published rate for the relevant financial year is used.

A figure in today's dollars is the figure in that year's dollars divided by the deflator at the end of that year. A flow that arrives mid-year is deflated by the deflator at the end of its own financial year, not by an average.
Every chart opens in the dollars actually in the account, and a switch on each chart restates everything in today's dollars. Switching it changes the display and nothing else: the tax and contribution rules stay as they were.
Set inflation to zero and the deflator stays at exactly 1.0. The before-inflation and after-inflation figures are then identical to the last bit rather than merely close, across 18,809 checked pairs.

The window rules

The tool replays the historical data rather than simulating it. It holds the user's portfolio mix through every stretch of history that the data can cover. It provides one result per starting year.

The engine only offers a starting year if figures are available for all asset classes included in the portfolio composition for every financial year within the time frame. A portfolio composition without fixed-term deposits is not subject to any restrictions imposed by the fixed-term deposit series, whereas a composition that does include fixed-term deposits is.
The engine does not offer any time window that extends beyond the last financial year in the data. It never extrapolates, forecasts or supplements a missing year.
If a value is missing, the engine rejects the time window rather than treating the gap as a zero return.
The engine then sorts the time periods by result. If there is an even number of time periods, it reports the higher of the two middle values as the median.

Term deposits

Term deposits work differently from all other products tracked by the engine, as the interest rate set for the year constitutes the annual return.

Every year on 1 July, a term deposit account is opened for twelve months at the one-year interest rate published at the end of the June just before. It is held until maturity and then renewed at the interest rate published at that time. The interest rate is fixed before the start of the year.
A term deposit is never valued at market value. There is no capital component added, so it continues to generate its interest rate even in a year when bond prices fall.
The total return consists of interest and is fully taxed: 15% in super accumulation, zero in a pension, and the marginal tax rate outside super.
There are no fund fees for a fixed-term deposit.
The series starts at FY1983. The published one-year interest rate begins in December 1981, so 30 June 1982 is the first end-of-June interest rate used by the calculation engine.
The engine takes into account neither illiquidity nor the continuation of an old interest rate when market rates change, nor early redemption charges. These three factors come into play if the money may be needed before the end of the term.

The checks behind the numbers

The same calculation exists in two places: in this browser-based engine and in the desktop tools this practice uses in its own work. A fixed results file is located alongside the code, and the browser engine's results are checked against this file. This amounts to a total of 361,621 checks, spread across 30 scenarios, a per-year grid of 180 windows, and 2,770 sell-out cases. Today, 0 of these checks disagree with the fixed file.

This was not the case during the reprogramming. Between 21 August and 4 September 2026, this engine differed from the desktop engine on five occasions. Each deviation was intentional and has been logged here along with the number of checks affected. The inflation rate for 2026 was finalised from 4.0942% to 3.9419% (2,022 checks). Fixed-term deposits were included in this engine, while the desktop engine does not include them (none, as the fixed file cannot recognise them). The A-REIT distribution split was added on 27 August (2,468; all in the single scenario holding listed property). The credit premium on the bond component was added on the same day and affected every scenario holding a bond (100,982). The contribution caps of 4 September were indexed to wages and rounded down to the nearest step, as the law requires (18,592). These four counts add up to the 124,064 discrepancies reported on this page on 4 September. On 5 September, the desktop engine adopted all of these with the exception of fixed-term deposits. Fixed-term deposits remain outside the fixed file and are instead checked according to their own rules (233 checks, all passed). On the same day, the fixed file was re-derived from the reconciled desktop engine, and the shared default-path fixture was locked again. Neither engine owns this fixture, and it was only locked again after both engines had matched the proposed file to the cent. Each of the five had been attributed the same way before the reconciliation. Putting the old value back made the checks it moved agree again exactly.

This reconciliation was a prerequisite for the launch of this website and was successfully completed. A future change to either engine is expected to change the fixed file again. The rule is now as follows: the two engines must match before a change is published; otherwise, this paragraph will describe the nature of the discrepancy and the reason for it.

Since September 2026, a visitor has been able to increase the annual amount either in line with wages or in line with inflation plus a margin. The wage series is AWOTE, average weekly ordinary time earnings. Since 10 October 2026, growth based on wages has been the default setting for every account type. The desktop engine increases a contribution exclusively by a fixed rate. The fixed file checks this fixed rate, and none of its scenarios take wages into account. The figures displayed by the tools by default are therefore based on a method that is not common to both engines. The checks mentioned above do not test it. Both engines read the same wage series to index the concessional cap.

Suite	Checks	What it holds
tests/run_default_path.mjs	2,426	the shared fixture. Three account types, the site's own first-load inputs, every valid 25 year window
tests/run_golden.mjs	359,195	the expanded grid: ending balances, contributions, tax paid, both capital gains regimes, money-weighted returns, the before-inflation pair, and every sell-out case
tests/check_term_deposits.mjs	233	term deposits: that the default is unchanged, that the sleeve computes, and that a window the series cannot cover is refused
tests/check_areit_and_credit.mjs	123	the A-REIT distribution split and the credit premium on the bond component: that the split is a split, that the default mix cannot see it, and that each parameter moves a figure in the direction and by the amount the research behind it measured

The limits of the engine

These are the limitations of the calculator:

The engine replays history. It doesn't forecast.
Returns are index returns less the fund fee. The engine makes no allowance for tracking difference, brokerage, spreads, or the cost of moving money.
Capital gains tax is not modelled along the way. It is modelled at disposal for accounts outside super only. The reason is that many super accumulation accounts are converted to tax-free allocated pension accounts.
Tax is at the account level. The engine holds no other income, offsets, deductions, losses carried forward, or family circumstances.
The income split per class is an assumption, not a series.
The engine applies today's rules across the whole of history. A window starting in 1971 is taxed under 2026 rules, apart from franking, which starts when imputation did.

About

Designed and produced by Dr Christoph Schnelle, In Your Interest Financial Planning. In Your Interest Financial Planning Pty Ltd, ABN 28 094 300 464 is Authorised Rep. No 308161 of Fiduciary Duty Advisers Pty Ltd AFSL No 527434. Nothing on this page is advice to you or to your clients. Corrections are welcome and very much appreciated – contact us.