House Flip Profit Calculator (Australia): Include Stamp Duty, Holding Costs and CGT

A house flip profit calculator is useful because it takes into account three lines that are usually excluded: stamp duty, holding costs and tax. Forgetting any of them in the calculation results in false optimism for the actual profit-making potential of the deal. These three factors are state-dependent, date-dependent and depends on whether the sale has been classified as trading or not by ATO.

This step 2 calculator sets out the specifications for a calculator incorporating all 3 aspects, and then populates the calculator with some test figures. These test calculations feature a $700,000 purchase price, $950,000 sale price, and $90,000 renovation costs. All figures in the test cases are for illustration purposes only and the rate tables have been taken from Revenue NSW, the Queensland Revenue Office and the ATO. The way this tax treatment is worked out is derived from this article, written by the ATO's former senior director Mark Chapman, in Money magazine and this article by tax adviser Matt Heron in API Magazine. This information is for general information only and should not be relied upon instead of advice from an accountant.

Want the maths run on your own deal? Start a free FlipSync IQ trial and test your first purchase price.

House Flip Profit Calculator Specification: Twelve Inputs

A calculator can be as accurate as the list of inputs is complete. The table below shows all the inputs with the ones needed for the example, and the default values used in the test cases.

Input	Test default	Why it belongs
State	NSW, then Queensland	Sets the stamp duty table
Purchase price	$700,000	Drives duty and cost base
Foreign purchaser flag	No	Queensland adds 8% for foreign persons buying residential land
Renovation budget	$90,000	The largest controllable cost
Sale price (ARV)	$950,000	The number every other line depends on
Selling costs	$25,000	Agent, marketing, and legal fees combined
Loan amount	$560,000 (80%)	Sets interest
Interest rate	7% interest-only	An assumption, not a quote
Other holding costs	$900 a month	Rates, insurance, utilities
Months held	6	The input that moves profit fastest
Other taxable income	$90,000	Sets your marginal rate
Tax treatment	Income, or capital gain	Decides whether the 50% discount applies

You can't plug in only four inputs to a calculator to answer a question that asks for twelve inputs. The next sections cover the missing three lines of input one at a time. 

House Flip Profit Calculator Rule One: Stamp Duty by State

Transfer duty is a lookup table, different in each state: Since we are looking at the 2026-2027 rates, and the rates page says that the rates start 1 July 2026. From what we have been told that there are thresholds in NSW that change every year, thus requires a dated table for examples. The normal rate for Queensland is $17,325 + $4.50 for each $100 over $540,000 up to $1,000,000, and for each and every part of hundred dollars.

Purchase price	NSW duty	Queensland duty	Gap
$700,000	$25,687	$24,525	$1,162

Calculations above are made from published brackets. Several technical problems, means the guide will not use Victoria. For Victorian transactions the user needs to refer to the calculator itself. In addition the levels of stamp duty change according to the contract date, hence the calculator needs to note this date used.

Here, duty comprises 3.7% of the NSW purchase price. This might seem tiny but it is 30 cents in every dollar from an $84,000 profit. As such, a house flip profit calculator can't include duty within the 'costs' column, it must be a standalone line item.

Curious how acquisition costs change your maximum purchase price? See how FlipSync IQ reverse-calculates your ceiling from your ARV and scope.

House Flip Profit Calculator Rule Two: Holding Costs Run on the Calendar

Generally, the costs of holding (costs) time are ignored in the spreadsheet calculations. Time-based costs also accumulate while no action is being taken.

Interest in the test case is $560,000 at 7%, or $3,267/month. In our test case we will add $900/month for rates, insurance & utility costs, bringing our total to $4,167/month, or $25,000 for six months. These figures are all assumptions and should be replaced with actual rate figures obtained from the lender and actual expenses.

The table below demonstrates the effect of time in the NSW transaction. Sale price, renovation and duty are all held constant while time is varied.

Months held	Holding costs	Pre-tax profit (NSW)
4	$16,667	$92,646
6	$25,000	$84,313
8	$33,333	$75,980
10	$41,667	$67,646
13	$54,167	$55,146

For each additional month, the cost is $4,167 or a 4.9% decrease compared to six months. The costs of various trade sequence or settlement delays may not be obvious at first but will add up in monthly increments. Most flippers overlook holding costs as they are relatively small in weekly terms.

A holding-cost line without a month count is a guess. A holding-cost line tied to the calendar is a forecast.

House Flip Profit Calculator Test Case: One Deal in NSW and Queensland

This is the full calculation process, because the order of operations is important as the stamp duty affects the profit which affects the tax.

Line	NSW case	Queensland case
Sale price	$950,000	$950,000
Purchase price	-$700,000	-$700,000
Stamp duty	-$25,687	-$24,525
Renovation	-$90,000	-$90,000
Holding costs (6 months)	-$25,000	-$25,000
Selling costs	-$25,000	-$25,000
Pre-tax profit	$84,313	$85,475
Break-even sale price	$865,687	$864,525

Break-even row is a good feature to add to any calculator. It shows what you will have to sell for to make no profit or loss. In the example in NSW, the buffer is 84,313 or 8.9% of the sale price. Check if you are close to selling at that price on realestate.com.au, domain.com.au or any other listing. Be aware that RP Data can be three months or more out of date.

There is little difference in the impact of the state switch between the two states since Queensland duty is only $1,162 lower, making the $3,447 or 1.4% difference in profits between the two states insignificant. Renovation and holding costs are significantly more important than the state's rate table in differentiating profitability. The state selector is there to save $1,000 and not $10,000.

However, the largest difference occurs after this as pre-tax profit is not how much they will keep.

House Flip Profit Calculator Rule Three: Which Tax Treatment Applies?

Whether a sale is categorized as a capital gain or as ordinary income is determined by the motives of the seller, as judged by the Australian Taxation Office (ATO). Chapman outlines the two main tests used by the ATO: the sale of an investment and a profit-making scheme. Heron, in API Magazine, details the criteria the ATO applies, which are motivation, volume, scale and reliance on property-flipping as a source of income.

There is a big consequence for profit-making scheme, as it will be taxed as ordinary income and will not attract the 50% CGT discount. However, an investor sale will apply, as long as the asset has been held for more than 12 months, in which case there is the exclusion of the acquisition day and day of the event. For CGT purposes, says the ATO, individuals and trusts are entitled to the discount, but companies are not. For the 'flippers' Heron says, like the taxable profit makers, they will lose the main-residence exemption.

For example, a property in New South Wales, with three different tax treatments. This example assumes an extra taxable income of $90,000 using the 2026-27 resident tax rates, 30 cents in the dollar on all income over $45,000, and 37 cents on all income above $135,000. And a Medicare levy of 2%. Offsets, surcharges and thresholds not taken into account in this example. Please note this is a calculator test. Actual results must be checked and verified by a licensed accountant.

Treatment	Months held	Pre-tax profit	Taxable amount	Tax and Medicare	Share of profit	After tax
Ordinary income	6	$84,313	$84,313	$29,732	35.3%	$54,581
Capital gain, no discount (held under 12 months)	6	$84,313	$84,313	$29,732	35.3%	$54,581
Capital gain with 50% discount	13	$55,146	$27,573	$8,823	16.0%	$46,323

The tax in the first two cases are the same because both are taxed at the marginal rate. Although the ATO may not see it this way, the cost to the individual is the same.

If you want to know what your tax set-aside is relative to your budget, Flip Sync IQ performs a free feasibility analysis giving you the ability to compare what was planned versus what happened.

House Flip Profit Calculator Test: Does Waiting for the CGT Discount Pay?

The third scenario is where the traps come in. Sure, in this case, 50% off seems like a good deal, because you pay less tax, but the following is a huge cost, which is seven extra months held at $4,167 per month, $29,167.

Comparing all of the options, the six-month sale seems to be the winner with an after-tax profit of $54,581, versus the 13month sale that has an after tax profit of $46,323. While the tax bill was reduced by roughly $20,900, the excess time we had to hold the asset was costly enough to give us a net loss of $8,258.

This result is also sensitive to inputs used in this example. Changes to marginal tax rates, markets, or holding costs may change the result. Therefore, it is better to incorporate such a comparison into the tool rather than argument over theoretically capable comparisons. The ideal house flip profit calculator would let one change the days of ownership and look up the after-tax numbers in either direction.

However, two things need to be said about the highlights. First, the discount is only acquired when ATO regards the sale as a capital gain; repeat flippers may not have such the advantage. Second, although a calculator is able to reflect the variations of several factors, it can't identify what sorts of treatment the ATO will apply. Talking with an accountant is suggested before a type of holding period is made.

The other variable is Goods and Services Tax (GST). According to heron, GST may need to be registered if turnover is above $75,000, or the significantly renovated property will be treated as a new residential property. It is worth clarifying GST before starting any renovation with your accountant.

How FlipSync IQ Works as a House Flip Profit Calculator

Flip Sync IQs' deal analyzer performs an ARV comparison with stepwise max purchase prices, instantly calculating your max offer. Margin protection is in place, so can automatically adjust the offer higher with additional Duty or longer timeframe prior to submission. At the footer of the site you'll find the Stamp Duty and Holding Cost Calculator, though its inputs haven't been checked in this demo.

Upon set-tlemnt, the project management platform records actual spend against the budget. Variance reports identify the divergence in a column of red and green for each budget line. Invoices and receipts are recorded against the budget along with the staged payments, whilst the holding costs are synced in to the project and the dynamic 'month in the table' counter can run. Pre-filled task lists help control the trade sequence. The return on investment (ROI) dashboard allows for an expected versus actual check. Permissions apply to user types (accounting partner or accountant), with view-only privileges whilst costs are settled and locked modules upon completion.

Ready to compare your forecast profit with your actual profit? Try FlipSync IQ free on your next flip.

House Flip Profit Calculator Checklist: Test Any Tool Against This Deal

Use any tools you prefer to run through the $700,000 purchase. One tool that is sufficiently similar to the New South Wales one within a few dollars will include duties, holding costs and the sequence. A tool that misses one of those areas shows its weakness.

Six investment calculator test questions: Does it differentiate by state? Does it list duty as a line-item? Does it connect holding costs to month number? Does it determine a break-even sale price? Does it charge tax at your tax rate? Does it let you see its tax assumptions? The vast majority of free calculators fall down on at least two of these counts. If a calculator isn't being clear about its assumptions, it can't be challenged, and a profit number that can't be verified is little better than speculation.

Choosing a House Flipping Calculator and a House Flip Profit Calculator

Choose a house flipping calculator that is transparent in its methodology. The best house flip profit calculator collects 12 inputs, computes duty by state, graphs holding costs against calendar time, and compares tax treatments side by side. This test case demonstrates why this matters. An $84,313 pre-tax profit becomes $54,581 after tax, while a 13-month hold to avoid the CGT discount results in $46,323.

Select one house flipping calculator, input the test case, and verify the output matches one of the above tables. Then review actual versus projection. Sign up for a free Flip Sync IQ trial and use your house flip profit calculator for your next deal, because the calculator you use should match your books, not your expectations.

Frequently Asked Questions

What should a house flip profit calculator include in Australia?

It must cover state stamp duty, a monthholding-cost-line, selling expenses and an estimate of tax. The test deal listed above has twelve inputs. Fewer suggests missing information.

How much is stamp duty on a $700,000 investment property? 

Calculations taken from published tables show stamp duty on a $700,000 investment property is ~$25,687 in New South Wales and ~$24,525 in Queensland. Victoria is not in these calculations so the State Revenue Office calculator should be used. Rates vary depending on contract date. 

Do I pay CGT or income tax when I flip a house? 

It is the determination by the ATO. While a profitable scheme attracts ordinary income tax, an investor sale is deemed as a capital gain, with 50% discount available only after a period of more than 12 months. It is best to seek out professional accounting advice. 

Is a house flipping calculator accurate for holding costs? 

Accuracy depends on the actual figures you input. A calculator that assumes a flat rate percentage ignores the details of how much the loan is, what the interest rate is and what the timeline for repayment is. Input actual interest and expenses for a period of four to ten months. 

Can I get the 50% CGT discount on a quick flip? 

If the holding period is less than 12 months you don't get it. The ATO does not count the acquisition day and event day. In the test case, you had to hold for more than 13 months to get the discount for the extra holding costs. 

Do companies get the CGT discount?

No, the ATO guide states that the discount is available to individuals and trusts but not to companies. The structure of your business should be considered – seek expert advice before you buy. 

How often should I rerun my house flipping calculator? 

Rerun it at each decision point: offer, contract, quote approval, and listing. Compare forecast with actual spend at every step. A house flipping calculator is a forecast, and forecasts drift.

Does a calculator replace an accountant? 

No. It models scenarios, and an accountant decides which tax treatment fits your history. Use the calculator to bring better questions to that meeting.