What Happens If You Miss the Self Assessment Deadline?

Late filing penalties

The penalty starts at £100 the day after the 31 January online deadline. After 3 months, HMRC adds £10 a day for up to 90 days (a maximum of £900). At 6 months a further charge applies of 5% of the tax due or £300, whichever is higher, and the same again at 12 months.

Late payment penalties and interest

Tax not paid by 31 January attracts a 5% penalty if still unpaid after 30 days, a further 5% after 6 months and another 5% after 12 months. HMRC also charges interest from the due date until you pay.

What to do now

File the return first, because that stops the filing penalties growing. Then pay what you owe or ask HMRC about a Time to Pay arrangement. If you had a genuine reason for being late, you can appeal the penalty.

Frequently asked questions

Do I pay a penalty if I owe no tax?

Yes. The £100 late filing penalty applies even when the return shows nothing to pay, although you can appeal if you have a reasonable excuse.

Can I get a penalty cancelled?

HMRC can cancel penalties where you had a reasonable excuse, such as serious illness or a bereavement, if you file promptly once the problem ends.