Free Tool · HMRC Penalties
Self Assessment Late
Penalty Calculator.
Enter your filing deadline, actual filing date, and tax owed. See your exact HMRC penalty — automatic charge, daily fines, surcharges, and interest — broken down line by line.
Calculate your penalty
£
The £100 automatic penalty applies even if you owe no tax.
Estimates based on HMRC SA370 guidance. Interest rate approximate at 7.5% p.a. Actual penalties may vary. Not a substitute for professional advice.
Key HMRC deadlines
31 JanOnline Self Assessment & payment
31 OctPaper return deadline
31 JulSecond payment on account
5 OctRegister for Self Assessment
Full HMRC tax calendar Can you appeal?
HMRC accepts appeals where you have a genuine reasonable excuse — serious illness, bereavement, or circumstances beyond your control. You have 30 days from the penalty notice to appeal.
HMRC Penalty Appeals serviceFile today. Stop the clock.
The only way to stop the penalty growing is to file. Our matched Harrow accountants can file your outstanding return within 24–48 hours.