UK tax tools · source checked
Self Assessment penalty: filing, payment, interest.
How do late-filing charges build up?
Late filing and late payment are separate. A return can attract filing charges even if no tax is payable. Read the GOV.UK penalty rules.
| Delay | Additional charge | How to read it |
|---|---|---|
| After the filing deadline | £100 | The initial fixed charge. |
| After 3 months | £10 per day, capped at £900 | Daily charges can be added to the initial charge. |
| After 6 months | 5% of tax due or £300, whichever is higher | A further charge, not a replacement for earlier charges. |
| After 12 months | Another 5% or £300, whichever is higher | Specific conduct can affect the final assessment; check the notice. |
What changes if the tax itself is unpaid?
| Delay | Charge at that point |
|---|---|
| 30 days | 5% of tax still unpaid |
| 6 months | A further 5% of tax still unpaid |
| 12 months | A further 5% of tax still unpaid |
These charges are separate from interest and any filing charges. Payment arrangements and the notice can affect the amount owed. Source: late-payment penalties.
Is the interest rate fixed for the tax year?
No. Interest can change during the period a balance is unpaid. On 2026-11-15, the applicable late-payment rate is 7.75%. HMRC has announced 8% from 24 November 2026; that rate is not yet effective on this page’s check date. Check HMRC’s dated rate table.
Read the rate periods and outstanding balance together. This page does not calculate an interest total or compound the penalty percentages into a personalised bill.
What if the notice looks wrong?
Compare the filing date, payment dates, outstanding balance and the tax year on the notice. If you have a reasonable excuse, the penalty guidance links to the appeal route. Use the notice’s instructions and retain evidence. A disagreement does not automatically erase the underlying return or payment obligation.
A late registration can instead involve a failure-to-notify assessment. Check that category before comparing it with the fixed filing table.
Questions answered on this page
Can a penalty apply when no tax is due?
Yes. Late filing can attract a fixed charge even when no tax is payable.
Are payment charges included in filing charges?
No. Late-payment charges and interest are separate from late-filing charges.