The UK capital gains tax calculator that shows its workingA free capital gains tax calculator for your broker exports, guides to HMRC's rules for shares, and an ERI lookup for offshore reporting funds.A free capital gains tax calculator for UK shares, options and ETFs. It works out what you owe for tax years 2018/19 to 2026/27 using HMRC share pooling rules.Sixteen brokers, one capital gains tax calculator for shares

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A generic CSV reader for any other broker, and the old cgtcalculator.com text format

HMRC's share matching rules, applied to every sale

Same-day rule: a disposal is matched first against anything bought on the same day (CG51560)

The 30-day "bed and breakfast" rule: then against anything bought in the next 30 days (CG51575)

Section 104 holding: whatever is left comes out of the pooled average cost