Key dates
For the 2025–26 tax year, most taxpayers must submit their online Self Assessment return by 11:59pm on 31 January 2027. Any balancing payment is generally due at the same time. Taxpayers who make Payments on Account may also need to make a second payment by 31 July, based on the normal Self Assessment rules.
A taxpayer who wants HMRC to collect an amount through their PAYE tax code must generally submit the online return by 30 December 2026, provided the relevant eligibility conditions are met. Paper returns for the 2025–26 year had to reach HMRC by 31 October 2026.
Information to assemble
Before starting the return, collect:
- P60, P45 and employment-benefit information.
- Bank and building-society interest statements.
- Dividend vouchers and investment income records.
- Sole-trader turnover, invoices, bank statements and allowable expenses.
- Property-income schedules, mortgage-interest information and repair records.
- Pension contributions, Gift Aid payments and relevant relief evidence.
- Capital gains calculations and records for disposals.
Do not rely solely on pre-populated information. HMRC’s use of third-party data is expanding, but taxpayers remain responsible for checking the return and reporting income correctly.
Payments on Account
Payments on Account are advance payments toward the following year’s tax bill. They commonly apply where the previous year’s Self Assessment liability exceeds £1,000, subject to the PAYE-related exception. If income has genuinely fallen, a taxpayer may request a reduction, but reducing the payments too far can result in interest on the shortfall.
For example, if a taxpayer’s previous liability was £8,000, the usual pattern may involve a £4,000 payment on 31 January and another £4,000 on 31 July, followed by a balancing payment after the return is calculated. The precise amount depends on the taxpayer’s circumstances and the composition of the liability.
Final review before submission
Use a reconciliation checklist:
- Compare bank interest and dividends with statements.
- Confirm that expense claims are business-related and evidenced.
- Check residency and foreign-income questions where relevant.
- Review the calculation before pressing submit.
- Save the submission confirmation and payment reference.
Filing early does not generally accelerate the payment deadline, but it gives the taxpayer time to budget, correct mistakes and contact HMRC or an adviser before 31 January 2027.