Tools

What will a late tax return cost me?

Penalties and interest for filing or paying your Self Assessment late, worked out date by date. And the July payment that catches people out.

Which return?

Have you filed it?

Have you paid the tax?

When will you file and pay what's left?

Try a few dates to see where the charges step up.

Your Self Assessment tax bill for the year (£)

The tax your return says you owe for the whole year, before any payments on account. A rough figure is fine.

Tax already taken through PAYE that year (£)

From your P60 or pension. Only used to check the 80% payments-on-account rule.

Did HMRC ask you for payments on account towards this year?

2025/26 return

If you file and pay on …

£0

Show your working

This is a guide, not tax advice. It uses HMRC's penalty rules for a personal return outside Making Tax Digital and today's late payment interest rate of 7.75% (Bank Rate + 4%), assumed to hold for future dates. It doesn't add interest on unpaid penalties, the higher penalties for deliberately withheld information, or the effect of a Time to Pay arrangement agreed before a penalty date (which can stop late-payment penalties). HMRC's own figures on your penalty notice are the ones that count. Nothing you type leaves this page. Read our 31 January Self Assessment checklist.