Capital Gains Tax Calculator

The annual exempt amount

Every individual has a tax-free annual exempt amount for capital gains, currently £3,000, deducted from your total gain before any CGT is calculated. Only the amount above that is taxable.

One set of rates for all assets

From 30 October 2024, the CGT rates for residential property and for other assets such as shares were aligned: 18% for any taxable gain that falls within your basic-rate band, and 24% for the slice above it. Before that date, property carried higher rates than shares — this calculator applies the current, aligned rates.

Why your other income matters

How much of your taxable gain is charged at 18% rather than 24% depends on how much of your basic-rate band is already used by your other income (salary, self-employed profit, rental income). Someone with little other income can have most of their gain taxed at the lower rate; someone already a higher-rate taxpayer has the whole gain taxed at 24%.

What counts as a disposal

CGT applies when you sell, gift, exchange, or otherwise dispose of an asset for more than you paid for it — this includes most residential property that isn't your main home, shares outside an ISA or pension, and other valuable assets. Your main home is usually covered by Private Residence Relief instead and doesn't need this calculator.

Reporting and paying

UK residential property gains must be reported and any tax paid within 60 days of completion, separately from your annual Self Assessment return — a much tighter deadline than other gains, which are reported on your next SA100. This calculator gives you the figure to plan for either route; ac-co's Self Assessment service can generate the actual submission.

A worked example

A landlord sells a rental property for a £60,000 gain, with £40,000 of other income for the year. After the £3,000 annual exempt amount, £57,000 is taxable. Their basic-rate band remaining after £40,000 of other income is £10,270 (up to the £50,270 threshold), so £10,270 of the gain is taxed at 18% and the remaining £46,730 at 24% — a total CGT bill of roughly £13,065, due within 60 days of completion.

Common mistakes to avoid

A frequent error is applying the higher rate to the whole gain once any part of it crosses into higher-rate territory — only the portion above your remaining basic-rate band is taxed at the higher rate, the rest stays at the lower rate. Another is missing the 60-day reporting deadline for UK residential property, which is separate from and much earlier than the normal Self Assessment deadline, and carries its own penalties for lateness. A third is forgetting that gains and losses on other assets sold in the same tax year can offset each other before the annual exempt amount is applied.

What counts as your gain

Your gain is the disposal proceeds minus what you originally paid, minus certain allowable costs of buying, improving and selling the asset (legal fees, stamp duty on the original purchase, capital improvements). This calculator takes the gain figure as a single input, so working out that starting figure correctly — including all the costs you're entitled to deduct — is the step to get right before using it.

Jointly owned assets

If an asset is owned jointly — with a spouse, partner, or other co-owner — each owner reports and pays CGT on their own share of the gain, using their own annual exempt amount and their own other income to determine the rate band, not a combined household figure. This calculator models a single individual's share of a gain; run it once per owner using each person's own share and other income for an accurate joint-ownership estimate.