Sharesight,
and UK CGT

Sharesight is a portfolio tracker, and by reputation a good one: performance over time, dividend tracking, contribution analysis, multi-currency holdings, broker imports. If that is what you need, none of what follows is an argument against it.

A UK Capital Gains Tax computation is a different job. It is not "what did this position return?" — it is a specific statutory calculation: Section 104 pooling, with the same-day and 30-day matching rules applied first and in order, per security, across every account you hold, with the result mapped onto the boxes of an SA108. A tool can be excellent at the first job and simply not do the second.

Rather than characterise anyone's product, here is exactly what we looked at. Checked 31 July 2026 — verify it yourself, and if it has changed since, tell us and this page will change.

• sharesight.com/uk/capital-gains-tax-report/ — a URL that would be the obvious home of a UK CGT report — returns HTTP 404.
• The sharesight.com/uk/ landing page links to tax reporting generally ("Investment Portfolio Tax Reporting") and names an Australian CGT calculator by name. On that page we found no mention of UK Section 104 pooling, the 30-day rule, or the SA108.

That is the evidence, and it is deliberately narrow: it is what two public pages said on one date. It is not a claim about what any product does internally, and we have not tested their software. If you are relying on any tool for a UK CGT figure — including ours — ask it these questions directly.

Useful whoever you end up using. A UK CGT calculation that cannot answer all five is not producing the number HMRC's rules produce:

1. Does it apply Section 104 pooling, rather than average cost per account or FIFO?
2. Does it apply the same-day and 30-day rules first, in HMRC's order, and show you when they bit?
3. Does it pool a security across every account and broker you hold it in — or one account at a time?
4. Does it give you SA108 box numbers, and the working behind each figure?
5. Does it handle the 30 October 2024 rate change mid-year, and the current annual exempt amount?

That last row is the honest trade. If you want one tool for both jobs, this is not it — plenty of people will reasonably keep a tracker for the year and use GainPool for the January calculation.

They are not mutually exclusive, and the join between them is your broker's export rather than either product. GainPool reads the transaction files your brokers already give you — the same files you would feed a tracker — so using it alongside one costs you nothing but the import.

Longstop Software is not affiliated with Sharesight, and Sharesight is a trade mark of its owner. Everything stated above about their public pages was checked on 31 July 2026 and is quoted with the URL so you can check it too; products change, and we would rather correct this page than leave it wrong — tell us. This is general information about how the UK rules work, not tax advice.