Capital Gains Tax Calculator UK Property
Model: gain = sale price − purchase price − allowable costs. Annual exempt amount £3,000 per person in 2026/27. The remaining gain is taxed at 18% up to the top of your unused basic-rate band (£37,700 of taxable income above the £12,570 personal allowance) and 24% above it. This is a simplified illustration for individuals, not tax advice. Losses, reliefs and non-resident rules are not covered.
How the tax is worked out, step by step
Capital Gains Tax is charged on the profit, not the sale price. The steps are: first, work out the gain by taking the sale price and subtracting what you paid for the property and the allowable costs — buying costs such as stamp duty and legal fees, selling costs such as estate agent and legal fees, and the cost of improvements that add value, like an extension (but not routine repairs or decoration). Second, subtract your annual exempt amount, which is £3,000 per person in 2026/27 — £6,000 for a jointly owned property, one allowance each. Third, split the remaining taxable gain by your income tax band: the part that fits inside your unused basic-rate band is taxed at 18%, and anything above it at 24%.
The worked example shows why your other income matters. With £30,000 of other income, your taxable income is £17,430 after the £12,570 personal allowance, so £20,270 of your basic-rate band is still unused. The first £20,270 of the taxable gain is taxed at 18% (£3,648.60) and the remaining £68,730 at 24% (£16,495.20), giving £20,143.80 in total. If your other income were £60,000, your basic-rate band would already be full, so the whole £89,000 would be taxed at 24% — £21,360. If you had no other income at all, £37,700 of the gain would be taxed at 18% and the rest at 24%, giving £19,098. The same property, three different tax bills — which is why the calculator asks for your other income.
The 60-day rule: do not miss it
If you sell a UK residential property and Capital Gains Tax is due, you must report the sale and pay the tax within 60 days of completion, using HMRC’s separate Capital Gains Tax on UK Property service — not at the normal Self Assessment deadline the following January. Missing the deadline can mean interest and penalties. If no tax is due, for example because the gain is covered by Private Residence Relief or the annual exempt amount, you generally do not need to make a 60-day report, but you may still need to report it on a Self Assessment return. The 60-day payment is an estimate based on the figures at completion; the final position is settled on your tax return, and you can claim back any overpayment.
Your main home is usually exempt
Private Residence Relief normally removes the gain on your only or main home from Capital Gains Tax altogether, so most people selling the home they live in pay nothing. The relief also covers the final 9 months of ownership even if you have moved out. It does not apply to a second home, a buy-to-let, or a property you have never lived in — those are exactly what this calculator is for. There are partial reliefs for homes that were your main home for part of the time, or that were partly let, and Lettings Relief can apply in limited cases where you shared your home with a tenant. Those cases are more complex than this calculator covers, so take advice if your home was let or only partly your main residence.
What you can deduct — and what you cannot
- You can deduct: the purchase price; stamp duty and legal fees on purchase; estate agent and legal fees on sale; and the cost of improvements that add value, such as an extension, a loft conversion or a new kitchen. Keep the invoices.
- You cannot deduct: routine repairs and maintenance, redecoration, mortgage interest, or the cost of your own time. Mortgage interest is a cost of borrowing, not a cost of the property.
- Losses: if you sell at a loss, the loss can be carried forward to offset future gains. This calculator does not cover losses.
- Joint ownership: each owner has their own £3,000 annual exempt amount and their own income tax band, which is why joint ownership often lowers the total bill — in the example, joint ownership cuts the tax from £20,143.80 to £19,423.80.
Capital Gains Tax rules change often — the rates were aligned to 18% and 24% for all assets from 6 April 2026 — so check the current GOV.UK guidance before you sell, and consider advice for large gains. The annual exempt amount is only £3,000, so even a modest gain can produce a tax bill, and the 60-day deadline comes sooner than most sellers expect.
Letting your former home: how the relief shrinks
The most common complicated case is a home you lived in and later let. Private Residence Relief covers the years you lived there as your main home, plus the final 9 months of ownership, but the years it was let are generally taxable. Suppose you bought a home for £150,000, lived in it for 10 years, let it for 10 years, and sold it for £350,000. The gain is £200,000, and roughly half of it — the let period minus the final 9 months — would be taxable, before the annual exempt amount. Lettings Relief can reduce the taxable gain in limited cases: it now only applies where you shared your home with a tenant while you lived there, and it is capped at the lower of the Private Residence Relief, £40,000, or the gain on the let part. Many sellers are surprised by how much tax is due on a former home, because the relief feels as though it should cover the whole gain. It does not. If you are thinking of letting your current home and buying another, get tax advice before you move out — the decisions you make in the first months of letting can change the tax bill years later, and some reliefs are lost once you stop living there.
Non-residents, trusts and other cases
This calculator covers UK resident individuals selling UK residential property. Non-UK residents pay Capital Gains Tax on UK property too, under the non-resident Capital Gains Tax rules, and must report the sale within 60 days whether or not tax is due — the rules are stricter than for residents, and the gain is usually calculated from the April 2015 value or the purchase price, whichever is later. Trustees and personal representatives pay a flat 24% on gains, with an annual exempt amount of £1,500 for most trusts (half the individual amount). Gifts are treated as disposals at market value, so giving a property to a child can trigger a tax bill even though no money changed hands — though transfers between spouses and civil partners are exempt. If a property is inherited, the gain is calculated from its value at the date of death, not from what the deceased paid for it. These cases are all outside this calculator’s scope, and getting them wrong is expensive, so take professional advice before selling, gifting or transferring a property in any of these situations.
Related: Stamp Duty Calculator · Rental Yield Calculator · Buy-to-Let Mortgage Calculator
Sources: GOV.UK “Capital Gains Tax rates”, “Capital Gains Tax allowances” and “Tax when you sell property” (60-day rule); HMRC HS283 Private Residence Relief. Checked 13 November 2026.