Written by Hammad Rasool MAAT·AAT licensed accountant·Updated November 2026

How much the penalty is

  • 1 day after the deadline: £200.
  • 3 months: another £200.
  • 6 months: HMRC estimates your Corporation Tax bill and adds a penalty of 10% of the unpaid tax.
  • 12 months: another 10% of any unpaid tax.

If your return is late 3 times in a row, the £200 penalties are increased to £1,000 each.

What a tax determination is

If the return is 6 months late, HMRC writes to tell you how much Corporation Tax it thinks you must pay. This is called a tax determination. You cannot appeal against it. The only way to replace HMRC's estimate with the real figure is to file the return and pay the Corporation Tax due. HMRC then recalculates the interest and penalties.

Key point: HMRC estimates are rarely in your favour. A determination should be treated as a deadline to file, not as a bill to argue about.

What to do when the letter arrives

  1. File the return: you must file the Company Tax Return before you can appeal the penalty, and filing stops the next penalty stage.
  2. Pay any Corporation Tax due: interest runs on late tax from the day after it was due.
  3. Decide whether to appeal: only if there was a genuine reason outside your control.
  4. Pay the penalty if there is no ground to appeal: unpaid penalties attract interest too.

How to appeal

You need a reasonable excuse for filing late. You can appeal online using the HMRC appeal service, or complete the form and post it to the address shown on it. The online form has to be completed in one sitting because it cannot be saved. You will need:

  • the company's Unique Taxpayer Reference
  • the date on the penalty notice
  • the penalty amount
  • the end date of the accounting period the penalty is for
  • an explanation of why the return was late
Example

A director was in hospital for 5 weeks around the filing deadline and was the only person able to approve the accounts. The return was filed 3 weeks late and a £200 penalty followed. The company filed, then appealed with the hospital dates as its reasonable excuse, and HMRC cancelled the penalty.

What does not usually count as a reasonable excuse

Relying on someone else who let you down, not knowing the deadline, finding the software difficult, or not having the money to pay an accountant are not normally accepted. Serious illness, bereavement, fire, flood and HMRC service failures are the kind of things that are.

Common questions

How much is the penalty for a late Company Tax Return?
£200 if it is 1 day late and another £200 at 3 months. At 6 months and again at 12 months HMRC adds 10% of the unpaid Corporation Tax.
Can I appeal a tax determination?
No. GOV.UK states that you cannot appeal against a tax determination. You replace it by filing the return and paying the tax due.
Can I appeal before I file the return?
No. You must file the Company Tax Return before appealing the late filing penalty.
Is this the same as a Companies House penalty?
No. Companies House charges its own penalties for late accounts. A company that is late with both will receive 2 separate penalties.

Checked against GOV.UK on 10 November 2026: Company Tax Returns: penalties for late filing.

About the author

Hammad Rasool MAAT is an AAT licensed accountant based in Bolton. TaxTune Accountants looks after sole traders, landlords, contractors and limited companies in Bolton, Wigan, Bury, Salford, Oldham, Stockport and Manchester, and online across the UK.