Capital gains tax on property

Private residence relief takes the gain on the home you live in out of tax altogether. If a property was your only or main home for the whole time you owned it, the relief covers the whole gain, you owe nothing, and you do not have to tell HMRC about the sale. That is why most people move house repeatedly without ever meeting capital gains tax.

The tax appears when the property was not your home for all of that time. The relief is then apportioned: the share of the ownership period it was your main home is relieved and the rest is not. The final nine months always count, whether you were living there or not, so that moving out before a sale completes does not cost you. That single rule is the difference between a large bill and a modest one for anybody who bought their next home before selling the last.

A property that was never your home gets none of this. A buy-to-let, a holiday home, an inherited house you let out: the whole gain is chargeable, and only the annual exempt amount comes off before tax.

Selling a UK residential property at a gain triggers a return and a payment within 60 days of completion, through a separate HMRC service called the Capital Gains Tax on UK property account. It is not part of your self assessment, and the deadline runs from completion rather than from the end of the tax year, so it can fall due many months before the return you were expecting to declare it on.

This catches people out constantly, because every other tax most of us meet is settled long after the event. Interest and a penalty apply if it is late. If the gain is fully covered by private residence relief, by the annual exempt amount, or by losses you had already realised before completion, no property return is required at all, though you can file one voluntarily.

You deduct what you paid for the property, the costs of buying it, the costs of selling it, and capital improvements. The costs of buying include the stamp duty you paid, which is worth knowing because it is often the largest single item and it is routinely forgotten years later. Improvements mean something that was not there before, such as an extension, not putting right something that wore out.

You cannot deduct mortgage interest, or the cost of arranging the mortgage, or normal maintenance such as repairs and decorating. HMRC's list of allowable costs is exhaustive rather than illustrative, so the test is not whether an expense felt necessary. Keep the completion statements from both ends of the ownership: reconstructing a purchase price and its costs a decade later is the part people find hardest.

This models the straightforward case, which is most cases: one person, resident in the UK, selling one UK residential property that was either a pure investment or a home for all or part of the time they owned it. The arithmetic behind it is the same as HMRC's and it is checked against their own worked examples.

It does not cover a property owned jointly or by spouses, who each have their own allowance and their own share of the gain. It does not cover lettings relief, which since 2020 only applies where you let part of a home while still living in another part of it. It does not cover part of a property used exclusively for business, grounds over half a hectare, a property held in a company or a trust, non-residents, gains reduced by losses brought forward, or a home you never actually moved into. Each of those changes the answer materially, and a calculator that quietly got one wrong on a five-figure bill would be worse than one that says so.

The rates, the annual exempt amount, the length of the final period exemption and the reporting deadline are not written into this website at all. They are held in CrestCast's admin config and read by this page from the same single source the CrestCast app uses, so there is deliberately no second copy to drift out of date. The basic-rate band the calculator uses to split the gain is the one the app already holds for income tax, rather than a second copy of the same number.

The published figures were checked against gov.uk on 03/09/2026. If they are not published for a tax year, this page shows nothing rather than a plausible-looking wrong number.

The sources are HMRC's own:

• Capital Gains Tax rates and how the gain is stacked on your income
• HS283: Private Residence Relief
• Report and pay Capital Gains Tax on UK property
• Work out your gain, and which costs are allowable