UK CT Late Filing Penalties: Doubled Rates Now on GOV.UK Guides

HMRC’s public Company Tax Return penalties guide now lists the increased flat-rate amounts that apply where the filing date is on or after 1 April 2026: £200 from the day after the deadline, another £200 if the return is still outstanding three months later, with £1,000 amounts where a company is late three times in a row. Tax-related penalties of 10% (and a further 10%) of unpaid tax can still apply when a return is six and twelve months late.

Those figures restore real-terms value eroded since the late-1990s rates. Finance Act 2026 amended Schedule 18 to Finance Act 1998 accordingly. This is not a new Budget announcement — it is an operational reminder for directors and agents clearing summer CT600s under the new tariff.

What changed — and what the July notice pause meant

For returns with filing dates up to 31 March 2026 the old £100 / £200 flat rates applied. From 1 April 2026 filing dates, the guide and CT211 notes show £200 / £400 (and £1,000 / £2,000 for successive failures). Paying Corporation Tax on time does not cancel a late-return penalty, and filing late still matters even when the tax bill is nil or already settled.

Agent Update 145 explained a temporary pause on automatic late-filing penalty notices while HMRC updated systems for the higher amounts — originally expected by 30 June and extended toward end-July 2026. The pause was about correct letter amounts, not a penalty holiday. Companies that filed late remain liable; expect notices to show the increased figures once automatic issuing is fully current.

Mid-August checklist for limited companies

Confirm your Company Tax Return filing date for the accounting period you are working on. Twelve months after the end of the accounting period remains the usual filing deadline — diary it separately from the nine-month Corporation Tax payment date.

If you previously relied on HMRC’s free online company accounts and tax return service, remember it closed at the end of March 2026. Most companies now need commercial software or an agent. Do not leave the first late return under the doubled tariff to a last-minute portal surprise.

Where a penalty notice arrives and you have a reasonable excuse, appeal online after filing the outstanding return — HMRC’s guide requires the return to be filed before you appeal the late-filing penalty.

How FinnAccountings helps with CT prep

Organised trial balances and working papers shorten CT600 review cycles. FinnAccountings helps UK and Irish limited companies prepare bookkeeping and corporation-tax packs with Chartered Accountant insight before you or your ICAEW/ACCA or Chartered Accountant (Ireland) adviser files. Start a free trial for review-ready drafts — we prepare packs; we do not submit CT600s to HMRC or pay Corporation Tax on your behalf.

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Related reading

For the summer system pause context and what agents told clients in July, read the notice-pause briefing.

UK CT late filing penalty notice pause (July 2026) →

If your filing workflow still assumes HMRC’s free CT600 portal, update process notes after the April 2026 closure.

HMRC free CT600 filing closed: what to do next →

Use the dual-market tax calculator for high-level planning estimates only — not a Corporation Tax computation or penalty estimate.

Open free tax calculator (Ireland & UK) →