What happens if I pay my Self Assessment bill late?
HMRC charges penalties of 5% of the tax unpaid at 30 days, 6 months and 12 months after the payment deadline. You are also charged interest on the amount owed. These are separate from the late filing penalties, so you can be charged both for the same tax year.
Figures checked against gov.uk on . General information, not tax advice.
At a glance
- 30 days after the deadline
- 5% of the tax unpaid
- 6 months after
- A further 5% of the tax unpaid
- 12 months after
- A further 5% of the tax unpaid
- Interest
- Charged on the amount owed
Why the first 30 days matter
The first percentage penalty arrives 30 days after the 31 January deadline, which is early March for a 2025/26 bill. Before then you are only charged interest, so contacting HMRC inside that window about a payment plan is better than letting the first penalty land.
Filing late and paying late are different breaches
Someone who files a day late but pays on time faces the filing penalty only. Someone who files on time but pays two months late faces payment penalties and interest, but not the filing charges. Missing both deadlines attracts both sets.
As with filing, a penalty can be cancelled if you had a reasonable excuse and acted as soon as you were able.