Guides
Each guide cites GOV.UK and marks what we could not verify. Last checked 17 October 2026.
Self Assessment Deadlines 2026-27: Key Dates
Self Assessment deadlines for the 2025 to 2026 tax year: 31 October 2026 (paper), 30 December, 31 January 2027, 31 July 2027, and 5 October registration.
Missed the 31 January Deadline? Penalties and Next Steps
Late Self Assessment penalties: £100, £10 a day up to £900, 5% or £300, and 5% of unpaid tax. GOV.UK calculator, appeals and next steps.
Payments on Account Explained, With a GOV.UK Example
Payments on account are two half-payments towards next year's bill, due 31 January and 31 July. When they apply, the balancing payment, an example.
How to Reduce Payments on Account: Online or SA303
Expect a lower tax bill? Ask HMRC to reduce payments on account online or with form SA303. What GOV.UK says and the interest risk if you guess low.
Registered for Self Assessment After 5 October? Your Dates
If you register after 5 October 2026, HMRC sends a later filing deadline (3 months from its letter) but tax is still due 31 January 2027. Penalty risks.
Do I Need to File a Self Assessment Return for 2025-26?
Who must send a Self Assessment return per GOV.UK: sole traders over £1,000, partners, Capital Gains Tax, Child Benefit Charge and more. Check tool.
Pay Your Self Assessment Bill: App, Bank or Tax Code
Ways to pay HMRC: bank transfer, card, Direct Debit, the HMRC app, payment plans and the tax code route (under £3,000, file online by 30 December).
MTD vs Self Assessment 2026-27: Who Is Affected?
How Making Tax Digital for Income Tax relates to Self Assessment: you still file for 2025-26, MTD from April 2026 above £50,000, April 2027 above £30,000.
Can't Pay Your Self Assessment Bill? Payment Plan Options
GOV.UK says you may be able to pay a tax bill in instalments. What you need, online limits reported by HMRC and what to do first.
Change a Self Assessment Return After Filing: 12-Month Rule
You can correct a filed return within 12 months of the deadline, online or on paper. After that you must write to HMRC. Dates for 2025-26 and refunds.
£1,000 Trading Allowance: Side Income and Self Assessment
GOV.UK's £1,000 trading allowance: when you may not need to tell HMRC, when you must register for Self Assessment, and the records to keep.
Lost Your UTR? Where to Find Your Self Assessment Number
A UTR is a 10-digit number you get after registering. GOV.UK says check your personal tax account, the HMRC app and old letters. Delivery times.