UK Capital Gains Tax Calculator 2026-27

What method does this tool use to work out the tax?

It subtracts the annual exempt amount from your gain (never going below zero), works out how much of the basic-rate band your other income has already used, and taxes the gain on top of that income. Gain inside the remaining band is charged at the lower rate and the rest at the higher rate. The asset-type input does not change the rates; the same two rates apply to every asset type, so enter one combined gain.

Which rates and allowances are built into the tool?

The tool carries a 2026-27 label and uses an annual exempt amount of £3,000, a personal allowance of £12,570 and a basic-rate band of £37,700 above it (so £50,270 in total). Gains are charged at 18% inside the remaining basic-rate band and 24% above it, for every asset type including shares and residential property. These are the figures built into this tool. UK rates and thresholds change at least every tax year on 6 April, sometimes part-way through a year, and the tool’s tables are not updated automatically, so HMRC or a qualified adviser governs what applies to your disposal.

How does it decide how much basic-rate band is left?

It takes your other taxable income, subtracts £12,570, floors the result at zero, and subtracts that from £37,700. With £30,000 of other income the remaining band is £20,270; with £60,000 it is nil, so the whole taxable gain is charged at the higher rate. No personal allowance taper is applied, pension relief is not modelled, and unused allowance cannot be set against the gain.

What happens if my gain is under the exempt amount, or is a loss?

Any gain at or below £3,000 returns £0 with a note that it is within the exempt amount, and the exempt amount shown is capped at the gain. A negative figure returns £0 with a note that there is no gain to tax. The tool does not carry losses forward or back, and it does not net several disposals; enter one net figure for the year.

What costs and reliefs does it take into account?

None directly. The gain box should hold a figure you have already worked out after purchase cost, allowable fees and improvement spend. Private residence relief, Business Asset Disposal Relief, rollover and deferral reliefs, spouse transfers, losses brought forward and the rules for non-residents are not modelled, and neither is any dividend or savings income in the band calculation.

What is the difference between the two percentage lines?

The effective rate divides the tax by the taxable gain (after the £3,000 exempt amount). The overall rate divides the same tax by the total gain before the exempt amount. For a £20,000 gain taxed entirely at 18%, the first line reads 18.0% and the second 15.3%. Both are display figures only and neither is a rate used in the calculation.

Does it differ for Scotland, Wales or Northern Ireland?

No. The tool asks only for other taxable income and asset type, and applies one set of CGT figures. Scottish income tax bands are not used to decide which of your income sits in the basic-rate band; the calculation uses the £37,700 band described above for everyone.

Does it show when the tax is due or how to report it?

No. It only returns an amount. Reporting routes, deadlines and payment dates for gains depend on the type of asset and your circumstances and are set out by HMRC, so check the current guidance before relying on any date.