Check your filing date

The 2025–26 tax year ran from 6 April 2025 to 5 April 2026. HMRC must receive a paper return by 31 October 2026 or an online return by 31 January 2027. You may be able to pay tax through your PAYE tax code if you already pay tax through PAYE, owe less than £3,000 and meet the other conditions. For that option, HMRC must receive a paper return by 31 October or an online return by 30 December 2026.

Sales and other business income

Bring together sales invoices, till receipts, payment processor statements, bank slips and records of cash received. Include all business income, including amounts paid through an online platform or into a personal account. Match receipts to sales records so you can explain refunds, differences or unpaid invoices.

Business costs

Collect supplier invoices, receipts, bank or card statements, petty cash records and mileage notes. Explain costs that could look personal and record private use where it affects an amount claimed. A payment record shows that you spent money; it does not decide whether the cost qualifies for tax relief.

Stock, work in progress and unpaid amounts

If you use traditional accounting, note what customers owed you at year end, bills received but not paid, the value of stock and work in progress, and the year-end bank balance. Keep the calculations behind those totals. Follow the records needed for your accounting basis.

Money you put into or take out of the business

Record money you introduced, drawings for personal use and business borrowing. This helps distinguish owner movements from sales and costs.

Other personal income and tax records

Self Assessment covers your personal tax position as well as your business. Gather relevant P60 or P45 information, pension statements, bank interest certificates, dividend statements and HMRC notices. If you receive rent, keep the property records too; this business checklist does not replace the separate property-income rules.

Reconcile before you file

  1. Match your sales list to invoices, cash records and payment statements.
  2. Match costs to receipts and bank or card entries.
  3. Check refunds, unpaid invoices, private use and money introduced or withdrawn.
  4. Confirm the figures cover 6 April 2025 to 5 April 2026, or make the required adjustment if your accounting period uses other dates.
  5. Keep your working papers. If you cannot obtain actual figures and use estimates or provisional amounts, tell HMRC and replace provisional amounts when you have final figures.

Keep records after filing

For a return due by 31 January 2027, keep business records for at least five years after that submission deadline, through at least the end of January 2032. If you send a return more than four years after its deadline, HMRC says to keep the records for 15 months after you submit it.

If you register for Self Assessment after 5 October 2026, HMRC will send a different filing date in a letter or email. That date is three months from the notice. Check it in your HMRC account. Tax due remains payable by the normal deadline.

Use these links to check a rate, deadline or eligibility rule.

Official sources

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