The Complete Self Assessment Guide
Everything you need to file your Self Assessment tax return — whether you're panicking with days to spare or planning ahead to never panic again.
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Self Assessment: Quick Answers
When is the Self Assessment deadline?
Online filing and payment are due by 31 January. Paper returns are due 31 October. If you've missed it, see ourmissed deadline guide.
What happens if I miss the Self Assessment deadline?
An automatic £100 penalty applies after one day, escalating to £10/day after three months and further surcharges at 6 and 12 months. Seewhat happens when you file late.
How do I file my Self Assessment tax return?
File online through your HMRC Government Gateway account, or use a filing service or accountant. New to Self Assessment? Start with ourfirst-year checklist.
Where can I get help with my Self Assessment?
Compare DIY, filing services, and accountants in ourSelf Assessment help section, or use our freeaccountant matching service.
What if I made a mistake on my Self Assessment?
You can amend your return up to a year after the filing deadline. See ourfixing mistakes guide for the step-by-step process.