The calculator is on the Home page.
UKCGT is a browser-based UK capital gains calculator for shares and funds. It lets you paste trades directly or load multiple .csv / .txt broker files, then converts supported broker formats into a common cgtcalculator.com-style trade list. Results should be identical to those of cgtcalculator.com, the well used and trusted CGT site, but my calculator accepts different and multiple .csv files without needing conversion.
The calculator applies the main HMRC share matching rules: same-day matching, 30-day bed-and-breakfast matching, and Section 104 pooling. It produces a tax-year summary, disposal-by-disposal calculations, and current Section 104 holdings. It does not calculate tax due, apply annual exemptions, carry forward losses, automatically adjust cost for ERI (but ETF ERI notional dividend payments can be looked up here and then pasted in manually as dividends and each dividend will be added onto the cost of the ETF to decrease your capital gain), spouse transfers, reorganisations, options or pre-6 April 2008 rules.
Supported inputs include Trading 212, Barclays .xls exports (saved as CSV), Interactive Investor, Lightyear/Sharesight, AJ Bell, and cgtcalculator.com text format. Multiple files in different broker formats should be selected in the file picker and trades are combined into one report. Duplicate Trading 212 and Interactive Investor rows are removed by looking for identical broker reference IDs, but try to avoid accidentally including duplicating trades if possible. You may be warned if identical trades are found – e.g. if you bought the exact same number of shares for the same price on the same day then you may have accidentally included a duplicate trade and are thus warned of this.
All processing runs locally in the user’s browser. The page does not submit trade data to the server – trade data does not leave your device.
The main script was written using Codex and ChatGPT 5. The website has been designed to be functional and easy to use (rather than pretty).