As of 13 August 2026, AI can only partly check whether you owe UK Capital Gains Tax on your investments.

What to actually do

1. Hand it to a person

   The route this page recommends

   A person who owns the outcome does this end to end, worth it when the failure is dear.

2. Use a tool built for this

   Second choice

3. Do it yourself

   The distant third

   A chat interface, chat-fluent skill, and roughly 1 hour until you can act on the result.

   How to actually do it

   1. Open your investment platform and bank records, then gather contract notes, annual tax statements, dividend information, and records of purchases, sales, transfers and fees for the relevant tax year.
   2. Create one line for every disposal in a spreadsheet, recording the asset, date, number of units, sale proceeds, purchase date, purchase cost and directly related fees.
   3. Mark any transaction involving a transfer, gift, inheritance, share split, merger, fund conversion, reinvested distribution or assets held across different accounts for separate checking.
   4. Open the relevant GOV.UK and HMRC Capital Gains Tax guidance and note the tax year, account type and any facts that may affect whether a disposal is taxable.
   5. Paste the cleaned spreadsheet and your notes into the prompt, leaving unknown figures blank rather than estimating them.
   6. Compare the model's transaction table and arithmetic with your statements and spreadsheet, then check every tax-treatment conclusion against the linked GOV.UK or HMRC guidance.
   7. Ask a UK tax adviser or accountant to check the calculation before reporting it if the records contain unusual transactions, missing acquisition costs, substantial losses, or any point you cannot verify.

   Prompt

   I am checking my UK Capital Gains Tax position for the tax year [tax year]. This is not professional advice. Use only the facts and transaction records I provide, and do not invent missing figures. First, create a clear table of each disposal with the asset, disposal date, proceeds, acquisition cost, allowable costs, and any relevant adjustment. Then calculate the provisional gain or loss for each disposal and show the arithmetic. Identify missing information, possible matching or pooling issues, transfers, corporate actions, or other details that could change the result. Separate facts, calculations, assumptions and questions. Use current GOV.UK and HMRC guidance where available, link to the relevant pages, and state when you cannot confirm the tax treatment. Do not give a confident yes or no if the records are incomplete. At the end, explain what I should check myself and whether I should ask a UK tax adviser or accountant before reporting anything. Here are my records and notes: [paste records and notes].

   Open it prefilled in ChatGPT or Claude, or copy it into Gemini, which takes no prefill link.