HMRC11 September 20265 min read

Corporation Tax late filing penalties doubled from April 2026

The fixed amounts were set in 1998 and have now doubled: a CT600 filed a day late costs £200, not £100. The new table, which returns it applies to, and what it means for your client list.

HMRC has raised the fixed penalties for filing a Company Tax Return late. They were set in 1998, and HMRC says inflation has since cut their real value to around half. The increase applies to returns whose filing date is on or after 1 April 2026, and it doubles every fixed amount.

The new penalty table

1 day late: £200 (was £100).
3 months late: a further £200, so £400 in total (was £200).
Late three times in a row: each fixed penalty rises to £1,000 (was £500).
6 months late: HMRC estimates the Corporation Tax bill and adds a tax-geared penalty of 10% of the unpaid tax.
12 months late: a further 10% of any unpaid tax.

Which returns does it apply to?

The trigger is the return's filing date, not the accounting period or the date the penalty is issued. A Company Tax Return is due 12 months after the end of the accounting period, so a company with a 31 March 2025 year-end had a return due by 31 March 2026 — old rates — while one with a 30 April 2025 year-end has a return due by 30 April 2026 and faces the new ones.

The filing date is not the payment date. Corporation Tax is paid nine months and one day after the period ends, three months before the return is due. Paying late runs up interest; these fixed penalties are about filing the return.

What it means for a practice

A missed CT600 now costs a client £200 on day one and £400 by month three, before any tax-geared penalty. A company that is late three times running pays £1,000 at each step — £2,000 in fixed penalties for a single return. Those are hard numbers to explain to a client, and they fall on the returns you already file every year.

How FilingKeeper reflects the change

FilingKeeper's Risk Center estimates the penalty for every overdue CT600 using the rate for that return's filing date: £200 or £400 from April 2026, £100 or £200 before. It shows the fixed part only, because the tax-geared part depends on figures FilingKeeper deliberately does not store.

Frequently asked questions

How much is the penalty for a late CT600 in 2026?

For a return due on or after 1 April 2026: £200 if it is up to 3 months late and £400 after 3 months. From 6 months HMRC adds 10% of any unpaid tax, and another 10% at 12 months.

When did the Corporation Tax late filing penalties change?

For Company Tax Returns whose filing date is on or after 1 April 2026.

What if a company files late three times in a row?

Each fixed penalty rises to £1,000, up from £500 before the change.

Sources: HMRC, "Increases to Corporation Tax late filing penalties", and GOV.UK, "Company Tax Returns: penalties for late filing". This article is general guidance, not tax advice.

Last checked against GOV.UK on 27 October 2026

Rules can change, so confirm on GOV.UK before you rely on a date or an amount. Sources:

Companies House Accounts Deadline: When Are Your Accounts Due?
When are annual accounts due at Companies House? First accounts: 21 months after registration. Later accounts: 9 months after year end. Includes worked examples.
Companies House Late Filing Penalty: What It Costs and How to Avoid It
Late accounts at Companies House cost £150 to £1,500 for a private company, and double if late two years running. See the full scale and how to avoid it.
Confirmation Statement Deadline: When Is Yours Due?
A confirmation statement must be filed at least every 12 months, up to 14 days after the review period ends. See how the date works, the fee and the penalty.