Tax & compliance
What is the corporation tax filing deadline?
By Kaiser Khan · Updated 13 August 2026
What are the three corporation tax deadlines?
Pay corporation tax within nine months and one day of the period end. File the CT600 within twelve months. File statutory accounts at Companies House within nine months of the financial year end. Payment is due before the return — finish the numbers early.
These are three different jobs, often three different systems. Missing the payment date costs interest even if the CT600 window is still open. Persistent late accounts can get a company struck off.
Is there a single national corporation tax deadline?
No. Unlike self assessment, everything runs from your company’s own year end. A 31 March 2026 year end means tax paid by 1 January 2027 and the CT600 filed by 31 March 2027. New companies and year-end changes can overlap periods.
That overlap is where an accountant earns the fee. Do not copy a neighbour’s January date onto your calendar unless you share a year end.
What are the penalties for a late CT600 or late accounts?
A late CT600 starts at £100, another £100 after three months, then tax-geared 10% penalties at six and twelve months. Companies House late accounts start at £150 and rise to £1,500 — doubled if you file late two years running.
File even if you cannot pay. Time to Pay is a conversation with HMRC; silence is a penalty. Dormant companies still have paperwork.
Is corporation tax moving to Making Tax Digital?
No. HMRC confirmed in its July 2025 Transformation Roadmap that it does not intend to introduce Making Tax Digital for Corporation Tax. CT600s are already filed online; no MTD quarterly reporting is coming for corporation tax.
Limited companies should still expect digital-first compliance in practice. VAT-registered companies already file VAT under MTD. Do not buy an MTD-for-CT product — it is not a thing.
People also ask
Do dormant companies have to file?
Yes. A dormant company still needs to file dormant accounts with Companies House each year, and must either file a CT600 or tell HMRC it is dormant so no return is required. Ignoring the paperwork leads to penalties even with no activity.
Can I file my own corporation tax return?
HMRC's online service allows it, and very simple micro companies sometimes manage. But the payment deadline falls before the filing deadline, computations have strict rules, and mistakes are costly — most directors use an accountant.
What if my company made a loss?
You still file the CT600 — losses can often be carried forward or back to reduce tax in other periods, but only if claimed through the return. The filing and Companies House deadlines apply whether or not tax is due.
This article is general information for UK businesses, not tax, legal, or financial advice, and thresholds change — confirm current rules on GOV.UK or with a qualified accountant before acting. Fee figures are indicative benchmarks from ourmethodology.