UK Capital Gains Tax Calculator - CGT Estimate

The UK Capital Gains Tax calculator estimates CGT on an asset disposal after cost basis, allowable costs, and the annual exempt amount. It is intended for planning share sales, fund disposals, crypto disposals, and residential property gains where a quick estimate is needed before using HMRC software or speaking with an adviser. The form separates the gain calculation from the rate selection so users can see both taxable gain and the tax rate applied. The mechanism is: taxable gain = max(0, sale proceeds - cost basis - allowable costs - annual exempt amount); estimated CGT = taxable gain x selected rate. The calculator uses a compact current-rate assumption of 18% for basic-rate taxpayers and 24% for higher or additional-rate taxpayers. It keeps the asset type selector visible because residential property remains an important search and planning refinement, but the simplified rate table applies the selected taxpayer rate rather than splitting gains across income bands. Use the calculator for pre-sale planning, checking whether the annual exempt amount removes a small gain, or estimating how much cash to reserve after a disposal. It is also useful for comparing a share sale and a property sale with the same gross gain, because allowable costs and taxpayer band often matter more than the sale price alone. The net gain after tax helps show the after-tax proceeds available for reinvestment or debt repayment. The estimate is not a filing engine. UK CGT can involve loss offsets, spouse transfers, private residence relief, business asset disposal relief, non-resident rules, crypto pooling, connected-party valuations, and deadlines for UK residential property reporting. For a return, confirm the tax year, allowance, reliefs, and band allocation against HMRC guidance. For best results, keep all inputs on the same time basis and currency basis, then save the assumptions beside the output. That practice makes the estimate easier to audit later and prevents a common spreadsheet error: mixing monthly values with annual values or combining before-tax and after-tax figures. Re-run the scenario with conservative and optimistic assumptions before using the result in a budget, filing decision, trade review, or transaction memo.