Self Assessment 2025/26: the records to gather now, not in January

The Self Assessment return for the 2025/26 tax year — 6 April 2025 to 5 April 2026 — is due online by 31 January 2027, with any tax owed on the same day. The form takes about an hour if you have the numbers. The reason it takes a week in January is that the numbers are spread across a year of bank statements, a folder of emails and a drawer, and every one of them is easier to find in September than in the last week of January, when HMRC's phone lines and your accountant's patience are both at their thinnest.

Here is everything the return might ask for, by source, so you can gather it now and file in October if you feel like it.

Dates first

• 5 October 2026 — the deadline to register for Self Assessment if this is your first year needing to file.
• 31 October 2026 — paper returns.
• 30 December 2026 — online filing deadline if you want tax under £3,000 collected through your PAYE code.
• 31 January 2027 — online filing, the balancing payment for 2025/26, and the first payment on account for 2026/27.
• 31 July 2027 — the second payment on account.

A return filed on 1 February carries an automatic £100 penalty, whether or not any tax is due.

The records, by source

Self-employment

• Business bank statements for the whole year — every account, every month. The bank statement is the spine of the self-employed pages; everything else is supporting detail. If your bookkeeping is behind, the minimal sole trader system gets a year's statements into categorised totals in a day, and the catch-up routine covers a backlog of more than one.
• Sales invoices or a sales list, to cross-check against bank receipts.
• Expense receipts, particularly for anything paid in cash or from a personal card.
• Mileage log, if you claim the flat rate for business miles.
• Home-working hours, if you use the simplified monthly allowance.
• Last year's return — the opening figures, the capital allowances pool, and any losses carried forward.

Property

• Rent received, by property — the letting agent's annual statement if you use one, otherwise the bank statements.
• Mortgage interest certificate from the lender: interest only, which is what the tax credit applies to.
• Expense records — repairs, insurance, agent fees, ground rent, service charges. The landlord guide categorises a year's statements into the property-page boxes directly.

Employment and pensions

• P60 from each employer at 5 April 2026, and a P45 from any job you left during the year.
• P11D for benefits in kind, if your employer still issues one (many now payroll benefits instead, in which case they're on the P60).
• Pension statements for private pension income, and the contribution certificates for personal contributions you're claiming higher-rate relief on.
• State pension — the annual letter, or the weekly amount times weeks paid.

Savings and investments

• Interest — HMRC pre-fills much of this from the banks, but check it against the statements; new accounts and some providers are missed.
• Dividend vouchers or the broker's annual tax summary.
• Capital gains — contract notes for shares or funds sold, completion statements for property, and the transaction history for crypto, which counts as a disposal every time one asset is swapped for another.

Everything else

• Gift Aid donations — the total for the year, and the declarations if you're a higher-rate taxpayer claiming the difference.
• Student loan — plan type and any repayments through PAYE (on the P60).
• Child Benefit received, if your income is over £60,000, for the High Income Child Benefit Charge.
• Marriage Allowance — whether a transfer is in place.
• Payments on account already made for 2025/26 — HMRC shows them in your online account; the January and July amounts are what you'll deduct from the balancing payment.
• Foreign income of any kind, with the foreign tax paid on it.

The bank statements are the slow part

Every line in that list except the bank statements is a single document you can find in ten minutes. The statements are different: they're the source for the self-employed and property pages, they need to be complete, and they need to become categorised totals. That's the job people leave until January, and it's the job that doesn't have to be slow any more.

Download the year's statements from online banking now — twelve per account — and convert them with NoRekey. Each statement becomes a spreadsheet in seconds, verified against its own opening and closing balances so you know every transaction is in it. Categorise into the boxes the return uses, total by category, and the self-employed and property pages are a transcription. Old or closed accounts? Here's how to get those statements — and the lead time is exactly why to ask now.

The last Self Assessment return, for some

If your self-employment and property income together exceed £50,000, you moved into Making Tax Digital for Income Tax on 6 April 2026. The 2025/26 return you're gathering records for is an ordinary Self Assessment return; the 2026/27 year is being reported quarterly instead, with a final declaration in place of a return. The MTD quarterly update guide covers the new routine — and the statement-conversion habit that makes this year's return easy is the same one that makes next year's quarters trivial.

Gather the list above this month. File in October, pay in January, and spend the last week of January watching other people panic.