Self Assessment
UK Self Assessment Guides by Tax Year
Self Assessment is the annual UK tax return run by HMRC for people whose tax cannot be collected in full through PAYE — the self-employed, landlords, high earners, company directors and anyone with significant untaxed income. You declare the income, HMRC works out (or you work out) the tax, and any balance is settled by 31 January following the tax year.
Pick a tax year below for the exact deadlines, penalty timeline and a step-by-step filing checklist for that year.
HMRC charges an automatic £100 the day after the deadline — even if you owe no tax. Daily £10 charges kick in after three months. See each year-specific page for the exact penalty dates.
Who must file a Self Assessment return?
You must register and file if, in the tax year, any of the following applied:
- You were self-employed as a sole trader and earned more than £1,000 (gross).
- You were a partner in a business partnership.
- You received rental income over £1,000 (gross) from UK or overseas property.
- You had untaxed savings, investment or dividend income over the relevant allowance.
- Your total income exceeded £150,000 (the threshold HMRC currently uses for mandatory SA).
- You or your partner claimed Child Benefit and one of you earned over £60,000 (HICBC).
- You received foreign income, capital gains above the annual exempt amount, or income from a trust.
- HMRC sent you a notice to file (form SA316) — once issued, you must file even if no tax is due.
Online vs paper deadlines
For every tax year ending 5 April, two deadlines apply:
- Paper return: 31 October following the end of the tax year (about 7 months after year-end).
- Online return: 31 January following the end of the tax year (about 10 months after year-end).
The same 31 January date is also the deadline to pay the balancing payment and the first payment on account. There is no extension for first-time filers — register with HMRC by 5 October to get your UTR in time.
Penalties for late filing
Penalties stack and apply even when no tax is owed:
- £100 the day after the deadline (automatic, fixed).
- £10 per day from day 91 (3 months late), capped at £900 over 90 days.
- £300 or 5% of tax due (whichever is greater) at 6 months late.
- Another £300 or 5% (whichever is greater) at 12 months late — higher in deliberate cases.
Late-payment interest also applies from 1 February onwards, currently at Bank of England base rate + 4%. A 5% surcharge on unpaid tax kicks in at 30 days, 6 months and 12 months. See gov.uk/self-assessment-tax-returns/penalties for the official table.
Payments on account explained
If your Self Assessment tax bill exceeds £1,000 and less than 80% of your tax is collected at source, HMRC requires payments on accounttowards next year's bill. Each payment is half of the previous year's total liability and falls due on 31 January (alongside the balancing payment) and 31 July.
If your income drops, you can apply to reduce the payments on account using form SA303 — but getting that wrong triggers interest on the shortfall.
Useful calculators
Estimate your liability before you file so the 31 January bill is not a surprise.
Think you overpaid in a previous year? See our tax refund guides — amendments and overpayment relief are available within HMRC's 4-year window.