What happens if I file my Self Assessment tax return late?

What happens if I file my Self Assessment tax return late? File your 2025-26 return online after 31 January 2027 and you get a £100 penalty straight away, then £10 a day after 3 months, and more at 6 and 12 months. Paying late adds 5% penalties and interest. Yes. Late filing and late payment are separate. The £100 penalty and the later filing penalties are charged because the return is late, even if the tax was paid on time. Usually not. GOV.UK says a payment that failed because you did not have enough money will not be accepted. For late payment penalties, HMRC's manual says a lack of funds only counts if it was caused by events outside your control. Usually 30 days from the date the penalty was issued. If you miss that, you will need to give a reason for appealing late. Read the full answer, with every source, at rightotax.co.uk.