The short version: SA370 is the form you use to appeal against Self Assessment penalties. If you filed or paid late and think you have a reasonable excuse, this is how you challenge the fine.
When can you appeal?
If something genuinely beyond your control prevented you from meeting the deadline. Serious illness, bereavement, HMRC system failures, natural disasters. “I forgot” doesn’t count.
How do you appeal?
Download SA370 from HMRC’s website, fill it in explaining what happened, and post it. For simple appeals against the initial £100 penalty, you can often do it online instead.
Should you still file?
Yes. Appeal or not, you still need to submit your return and pay what you owe as soon as possible. The appeal is just about the penalty, not the underlying obligation.
Got a penalty you want to challenge? We can help you put together your appeal.
