Quick answer
Follow the instructions in the penalty letter to appeal. You can appeal penalty points, the £200 late submission penalty and late payment penalties. You usually need to appeal within 30 days of the date on the notice, and to show a reasonable excuse for missing the deadline.
What you can appeal
A penalty point for a missed deadline
A £200 late submission penalty
A late payment penalty
What counts as a reasonable excuse
Something unexpected or outside your control that stopped you meeting the deadline. Examples HMRC typically accepts include:
serious illness, or the death of a close relative, shortly before the deadline
a fire, flood or theft that stopped you getting to your records
failures in HMRC’s own systems or your software that you couldn’t reasonably avoid
Forgetting, relying on someone else, or not having the money usually aren’t accepted on their own.
How to appeal
Read the penalty letter for the appeal route.
Appeal within 30 days of the date on the notice.
Explain what happened, when, and how it stopped you.
Send the missing submission as soon as you can.