Corporation Tax Late-Filing Penalties Have Doubled: What Company Directors Need to Know

HM Revenue & Customs has started issuing corporation tax late-filing penalty notices again after a pause in its systems, and at the same time the penalties themselves have got noticeably more expensive. If your company's accounting period ends on or after 6 April 2026, missing the corporation tax return deadline now costs twice what it used to.

What's changed

The flat-rate penalty for filing a company tax return (CT600) even one day late has risen from £100 to £200. File three months late and there's a further £200 on top, previously £100, so three months late now means £400 in flat penalties alone, up from £200. The percentage-based surcharges that kick in at six and twelve months, calculated on HMRC's own estimate of what you owe, haven't changed, but those estimates tend to run high. Miss the deadline for two accounting periods in a row and the initial penalty doubles again, to £400. These are the first changes to corporation tax late-filing penalties since 1998.

Why this matters right now

HMRC had paused sending out late-filing penalty notices for a period and has now resumed issuing them, working through a backlog. Company directors who assumed a missed deadline had gone unnoticed, or who filed late without hearing anything back, may find a notice arriving that reflects the new, higher rates if it relates to an accounting period ending on or after 6 April 2026.

The deadlines, as a reminder

A company tax return is due 12 months after the end of the accounting period it covers. Corporation tax itself is normally due earlier, 9 months and 1 day after the end of the accounting period, for companies not on the quarterly instalment regime. It's easy to conflate the two: filing on time doesn't help if the tax itself was paid late, and vice versa, since interest on late payment runs separately from the late-filing penalty.

What to check now

If you run a limited company, it's worth a quick check: when does your current accounting period end, and are both the payment date and the 12-month filing deadline noted separately? If you've had a change of accounting reference date, a dormant period, or a first year in business, the deadlines can fall in less obvious places, so it's worth confirming rather than assuming. If a return is already overdue, filing it as soon as possible limits further penalties, even though the initial one will already apply.

If you're unsure where your company stands, or want a second pair of eyes on your filing dates, get in touch with Jackson Lee Accountants in Bury, Greater Manchester, and we'll help you check.