This calculator works out Irish tax

It applies Revenue's rules — a 33% rate, the €1,270 exemption, fund exit tax and a 31 December year end. None of that is how a UK return is worked out, so running your figures through it would give you a confident answer to the wrong question.

Pegora does compute UK capital gains — the Section 104 pool, the same-day and 30-day matching rules, and the 18% and 24% rates against your income — inside an account, where we can see enough of your history to get the matching right. A single uploaded file is not enough for that: the 30-day rule reaches into the following tax year.