SA370: appeal a Self Assessment late filing or payment penalty

Who needs it

• Anyone who received a Self Assessment late filing or late payment penalty and had a reasonable excuse for missing the deadline.
• People who disagree that the penalty is due at all.
• Not people who no longer need to send a return: they can ask HMRC to cancel the penalty instead.

What you need before you start

• The date the penalty was issued.
• The date you filed your return and the date you paid your tax, if you have.
• Details of your reasonable excuse, with dates showing when it started and ended.
• Your name and Unique Taxpayer Reference (UTR).

How to file SA370

1. 1Use HMRC's online checker to see how to appeal your penalty.
2. 2File the return or pay the tax as soon as you're able, if you haven't already.
3. 3Appeal online, or download form SA370 or SA371 and appeal by post. If you have the appeal form that came with your penalty letter, you can use that.
4. 4Consider paying the penalty while you wait. If your appeal fails, interest runs on an unpaid penalty from the date it was due.
5. 5If you disagree with HMRC's decision, ask for a review.

The penalties you can appeal

For a late return HMRC charges a £100 penalty straight away. After three months, daily penalties of £10 a day start, up to £900. After six months, there's a further penalty of 5% of the tax due or £300, whichever is higher, and the same again after 12 months.

Late payment brings separate penalties of 5% of the unpaid tax at 30 days, six months and 12 months, plus interest on the amount owed. You can appeal any of these if you have a reasonable excuse.

What counts as a reasonable excuse

HMRC's examples include a partner or close relative dying shortly before the deadline, an unexpected stay in hospital, a serious or life-threatening illness, your computer or software failing while you prepared an online return, problems with HMRC's online services, fire, flood or theft, unforeseeable postal delays, delays related to a disability or mental illness, and relying on someone else who didn't send your return.

HMRC usually doesn't accept a bounced cheque or failed payment through lack of funds, finding its online system too difficult, not getting a reminder, or making a mistake on the return. Whatever the excuse, you must send the return or payment as soon as you're able.

After you appeal

If HMRC agrees your appeal, it repays any penalty you paid, with interest, provided you have no other tax outstanding. If it doesn't, you can ask HMRC to review the decision. HMRC publishes guidance on when to expect a reply.

Common mistakes

• Giving an excuse HMRC doesn't usually accept: not getting a reminder, finding the online system too difficult, a payment failing for lack of funds, or making a mistake on the return.
• Appealing without dates. HMRC's guidance asks you to explain why it was late, with dates.
• Leaving the penalty unpaid during the appeal. If HMRC rejects the appeal, you pay interest on it from the date it was due.
• Missing the 30-day window and not explaining why. HMRC asks for a reason for the delay.