What happens if you file Self Assessment late?

Late filing penalties

If you need to file a Self Assessment tax return and miss the deadline, HMRC can charge an initial £100 late filing penalty. Further penalties can build up if the return remains outstanding.

• After 3 months: daily penalties of £10 per day, up to £900.
• After 6 months: 5% of the tax due or £300, whichever is greater.
• After 12 months: another 5% or £300 charge, whichever is greater.

Late payment penalties and interest

Filing late and paying late are separate issues. If tax remains unpaid, HMRC can charge late payment penalties at 30 days, 6 months and 12 months, plus interest on the amount outstanding.

What to do if you are already late

• File the return as soon as possible, even if you cannot pay the full bill immediately.
• Pay what you can to reduce interest and late payment exposure.
• Check whether a Time to Pay arrangement is available if you cannot clear the balance.
• Appeal only where you have a genuine reasonable excuse and evidence to support it.

How RR Accountants can help

We can help reconstruct missing records, file overdue returns, explain what HMRC is charging and put a practical filing calendar in place so the same problem does not repeat next year.

For the official penalty rules, see GOV.UK guidance on Self Assessment penalties.