A Sydney investor who converted their home to a rental in 2020 discovered an old agent appraisal in their email archive last year. That four-year-old document reduced their taxable income by $60,000 when they sold. The mechanic is simple, the timing is critical, and most people miss it.
When you convert an owner-occupied property to an investment, your cost base for capital gains tax purposes resets to the market value on the day of conversion, not what you originally paid for it. The ATO allows this because you’ve only been able to claim depreciation and other deductions from that point forward. The problem: most investors use their bank’s valuation from the refinance they did to pull equity for the next purchase. Banks price for risk and lend conservatively. That low number becomes your new cost base, and every dollar of gap between the bank figure and true market value gets taxed when you sell.
How the $60,000 gap opened
The investor’s bank valued the property conservatively when they refinanced to buy their next home in 2020. Five years later, they sold for $520,000 more than that bank figure. Under the old 50 per cent CGT discount, that meant tax on a $260,000 gain. Their accountant asked whether they’d used a rental agent when the property converted. They had, and that agent had provided a market appraisal at engagement in case the investor wanted to sell. The appraisal sat in an email folder for five years. It came in $120,000 higher than the bank’s valuation. The ATO accepts independent agent appraisals as evidence of market value at conversion, so the taxable gain dropped to $200,000. At marginal rates near 47 per cent for high earners, that $60,000 of taxable income saved roughly $28,000 in actual tax paid.
The mechanic works because capital gains tax is calculated from your cost base, and for converted properties the cost base is market value at conversion, not purchase price. If you don’t document that value independently, the ATO and your accountant fall back on whatever valuation you have on file. For most people, that’s the bank’s conservative figure from the refinance loan application. The difference is pure tax leakage.
The new pressure point
The 50 per cent CGT discount for investment properties held over 12 months was removed in the May 2025 federal budget. Properties purchased or converted after budget night now pay tax on 100 per cent of the gain. For anyone who already held an investment property before that date, the gain gets split: the portion that accrued while the discount was still in place gets taxed at 50 per cent, the portion after budget night gets taxed in full. The valuation you hold on file as at budget night determines where that line sits.
If you converted a property years ago and only have a low bank valuation, the ATO may assume more of the gain happened in the post-discount period unless you can prove otherwise. If you’re holding an investment property now and plan to sell in five or ten years, get an independent valuation dated as close to budget night as possible and keep it on file. The cost is a few hundred dollars. The tax saved could be five figures.
The catch
- Bank valuations are designed to protect lenders, not maximise your cost base, they routinely come in 5–15 per cent below true market value
- Most investors don’t think about CGT until they sell, by which point it’s too late to backdate a valuation
- Agent appraisals from the time of conversion are accepted by the ATO, but only if you actually obtained one and kept the record
- If you converted pre-budget-night and don’t have an independent valuation, you may pay full-rate CGT on gains that actually occurred during the discount period
Red flags for the next 12 months
Anyone converting a property to an investment in 2025 or later: request a written market appraisal from at least one agent before you sign the rental management agreement. Email it to yourself and your accountant with the subject line “Market valuation at conversion [address] [date]” so you can find it in five years. Do not rely on the bank’s valuation from your refinance. The bank’s number is for the bank’s risk, not your tax position.
Anyone who already holds an investment property purchased or converted before May 2025: commission an independent valuation now, dated as close to budget night as practical, and file it with your tax records. If you sell in 2030 and the market has doubled, you’ll want proof that half that gain occurred while the discount still applied.
Anyone who converted a property in the past few years and only has a bank valuation: check whether your rental agent provided a market appraisal at engagement. Check your email archive, your agent’s client portal, any onboarding documents. If you find one and it’s higher than the bank figure, send it to your accountant now and confirm they’ll use it as your cost base. If you can’t find one, you’re stuck with the bank’s number unless you can produce another form of independent evidence from the time of conversion (a comparable sales report, a buyer’s agent appraisal, a written CMA from a second agent).
What to do next
If you’re converting a property now: get a written market appraisal from an agent or valuer, dated the week of conversion, and store it with your loan and tax files. Cost: $0–$500 depending on whether your agent provides it free at engagement or you pay a valuer. Potential tax saved: tens of thousands at sale.
If you’re holding a pre-budget-night investment property: commission a formal valuation dated May 2025 and keep it on file. If you’re not selling soon, this is optional but cheap insurance. If you are selling in the next 2–3 years, it’s essential.
If you converted in the past and can’t find an independent appraisal: accept that your cost base is the bank’s figure and factor that into your hold-or-sell decision. The tax wedge may change the timing of your exit or the yield hurdle you need to stay in.
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General info, not financial advice.
