How to Use AI to Prepare Your Self Assessment Tax Return

If you’re self-employed, a landlord, earn money from a side hustle or have other income that isn’t taxed through PAYE, you’ll probably need to file a Self Assessment tax return with HMRC. For the 2025 to 2026 tax year, the online deadline is 11:59pm on 31 January 2027, and that’s also when any tax you owe is due. Every January, thousands of people leave it to the last week and scramble to find paperwork.

AI can’t file your return for you, and it isn’t a tax adviser. What it can do is help you get organised early: make a checklist of what to gather, sort your income and expenses into sensible categories, explain HMRC jargon in plain English and turn your questions into a clear list for an accountant. This guide takes about an hour to set up, plus the time it takes to gather your records.

New to AI? Start with our beginner’s guide.

What you’ll need

• Your Government Gateway login for your HMRC online account (and your UTR number)
• Records for 6 April 2025 to 5 April 2026: invoices, bank statements, receipts, P60 or P45, rental statements, pension and savings interest details
• A spreadsheet or notes app
• An AI chatbot, used with personal details removed
• About an hour to start, plus gathering time

Step-by-step: get your tax return ready with AI

1. Check you need to file. If you’re unsure, use HMRC’s online checker on GOV.UK. Ask the AI to explain the result in plain English, but rely on GOV.UK for the decision.
2. Make a personal checklist. Describe your situation (without names or account numbers) and ask for a list of records to gather and deadlines to note (prompt 1).
3. Gather and anonymise your records. Export bank statements and invoices. Before pasting anything into AI, remove names, addresses, account numbers and your UTR.
4. Sort income and expenses. Paste anonymised transactions and ask the AI to categorise them and to list anything it’s unsure about separately (prompt 2). Check every uncertain item against HMRC’s guidance on allowable expenses.
5. Understand the terms. Ask the AI to explain anything confusing, such as the trading allowance, simplified expenses, payments on account or Class 4 National Insurance (prompt 3). Confirm the details on GOV.UK, as rules and thresholds change.
6. Do a rough estimate. Ask for a simple estimate of profit and likely tax so you’re not surprised, but treat HMRC’s calculation as the real figure.
7. Prepare questions for an accountant. If anything is complicated, ask the AI to turn your notes into a short, clear list of questions (prompt 4).
8. File and pay yourself. Log in to your HMRC online account, enter your figures, check the summary and submit. Note your payment reference and pay by 31 January.

Copy-paste prompts

1. Build my Self Assessment checklist

I live in the UK and need to prepare my Self Assessment tax return for 6 April 2025 to 5 April 2026. My situation: [EMPLOYED AND SELF-EMPLOYED / LANDLORD / SIDE HUSTLE / OTHER INCOME]. My income sources are [LIST, NO PERSONAL DETAILS].
Make a checklist of the records and figures I'll need, grouped by income source, plus key deadlines. Point out anything I should check on GOV.UK because it depends on my circumstances.

2. Categorise my income and expenses

Here are my anonymised business transactions for the tax year: [PASTE DATE, DESCRIPTION, AMOUNT].
Sort them into income and expense categories that match HMRC's self-employed expense types, as a table with totals. List separately any items that might be personal, partly personal or not allowable, and explain why so I can check them.

3. Explain the jargon

Explain these Self Assessment terms in plain British English, with a simple example for someone in my situation ([SITUATION]): [TERMS, SUCH AS TRADING ALLOWANCE, PAYMENTS ON ACCOUNT, SIMPLIFIED EXPENSES]. Tell me which GOV.UK pages I should read to confirm the current rules.

4. Questions for my accountant

Here are my notes about my tax year: [NOTES]. Turn them into a short, numbered list of clear questions for an accountant, grouped by topic, with the figures or documents I should bring for each one.

Recommended tools

• ChatGPT: good for checklists, categorising transactions and explaining terms step by step.
• Claude: handles long lists of transactions well and is careful about flagging uncertainty.
• Gemini: works well with spreadsheets in Google Sheets for sorting and totalling.
• Grok: quick plain-English explanations when you’re stuck on a term.
• HMRC’s online service and GOV.UK: the only places to check rules and file your return.

If your records are a mess, start with our guide to organising receipts and expenses as a freelancer, and if your extra income comes from a side business, read how to manage side hustle income with AI. HMRC letters can be confusing, so see how to understand official letters and forms, and learn to spot scam emails and texts, as fake tax refund messages are common at this time of year.

Tips and mistakes to avoid

• Never share personal identifiers. Remove your name, address, UTR, National Insurance number and bank details before pasting anything.
• Rules change. AI may give out-of-date thresholds or rates. Check every number on GOV.UK.
• Don’t guess at expenses. Only claim what you can back up and what HMRC allows.
• Start early. Gathering records always takes longer than you think. Aim to file by December.
• Beware of scams. HMRC won’t text or email you about tax refunds with a link to click. If in doubt, log in to your account directly.
• Check Making Tax Digital. If your self-employment or property income is high enough, Making Tax Digital for Income Tax may apply to you. Check GOV.UK.
• Get help when it’s complex. Capital gains, foreign income or several businesses are worth an accountant.

FAQ

Can AI fill in my tax return?

No. You enter and submit your figures through HMRC’s online service or approved software. AI can help you organise and understand them first.

Is it safe to use AI with my financial information?

Only use anonymised figures, with names, numbers and references removed, and check your AI tool’s privacy settings.

When is the deadline?

For the 2025 to 2026 tax year, online returns and payment are due by 11:59pm on 31 January 2027. Paper returns were due by 31 October 2026.

What if AI tells me something different from GOV.UK?

Trust GOV.UK or a qualified adviser. AI can be wrong or out of date on tax rules.

I live in the UK and need to prepare my Self Assessment tax return for 6 April 2025 to 5 April 2026. My situation: [EMPLOYED AND SELF-EMPLOYED / LANDLORD / SIDE HUSTLE / OTHER INCOME]. My income sources are [LIST, NO PERSONAL DETAILS].
Make a checklist of the records and figures I'll need, grouped by income source, plus key deadlines. Point out anything I should check on GOV.UK because it depends on my circumstances.

Related guides

• How to use AI to track your spending
• How to use AI to prepare for a meeting with a financial adviser
• How to use AI to understand your payslip

Reference: GOV.UK: Self Assessment tax returns