As of 13 August 2026, AI can only partly calculate your Self Assessment tax bill.

What to actually do

1. Hand it to a person

   The route this page recommends

   Someone with a licence or accountable authority has to sign this before it counts.

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 HMRC records and gather the tax year, tax reference details, employment P60 or P45 figures, payslips, pension information and records of tax already deducted.
   2. Gather your self-employed accounts, invoices, expense records, property income, dividend statements, savings interest, benefits, pension contributions, student loan details and any capital gains information that may belong in the return.
   3. Open GOV.UK guidance for Self Assessment and save the relevant pages for the tax year, including income tax, National Insurance, allowable expenses, payments on account and any relevant allowances.
   4. Remove account numbers and other unnecessary private information, then paste the remaining figures and the copyable prompt into a chatbot.
   5. Ask the chatbot to produce the provisional calculation, list missing information, show each step and separate the amount due from any payments on account.
   6. Compare every input and rule in the response with your records and the current GOV.UK pages, and recalculate the arithmetic independently.
   7. Send the figures, assumptions and unresolved questions to a qualified tax adviser or accountant before using the result in your Self Assessment return.

   Prompt

   Calculate a provisional UK Self Assessment tax bill for the tax year [TAX YEAR] using only the information I provide below and the current rules published on GOV.UK. Do not invent, estimate or fill in missing figures. First list every figure you used and every figure that is missing. Separate employment income, self-employed income and allowable expenses, dividends, savings income, pension contributions, benefits, property income, capital gains, student loan details, tax already deducted, payments on account and any other relevant items. State which assumptions or tax treatments need confirmation. Show the calculation step by step, including bands, rates, allowances and deductions, and give a separate result for income tax, National Insurance if relevant, capital gains tax if relevant, payments on account and the remaining amount due. If the information is insufficient, give a range or separate scenarios rather than one confident total. Link to the relevant GOV.UK pages for each rule you rely on, identify rules that may have changed, and finish with a checklist of questions for a UK tax adviser or accountant. This is not professional advice. Here are my records and figures: [PASTE YOUR INFORMATION HERE].

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