Corporation Tax Return & Payment Deadlines Check

Why this matters

Limited companies must pay Corporation Tax and file a company tax return (CT600) with HMRC, and the two deadlines are different. Under the Corporation Tax Act 2010 and Finance Act 1998 Schedule 18, tax for smaller companies is normally due 9 months and 1 day after the end of the accounting period, while the CT600 and accounts must be filed within 12 months of the period end. HMRC does not send a payment reminder or tell you the amount due, so the company must calculate its own liability. For a company with a 31 March 2026 year-end, payment is due by 1 January 2027 and the return by 31 March 2027. Missing these dates is costly. A late CT600 attracts an automatic £100 penalty, rising to £200 if it is more than three months late, with higher fixed penalties if the return is late three times in a row and further tax-geared penalties of 10% of unpaid tax at 18 months. Late payment brings interest from the due date. Companies with profits above £1.5 million must pay in quarterly instalments, and the rate depends on profit levels, with small profits taxed at 19% up to £50,000, main rate 25% above £250,000 and marginal relief in between. Errors in expenses, capital allowances or director loan accounts can also trigger HMRC enquiries, so accurate records and early preparation matter.

What you'll need

• Whether your company is a UK-resident limited company with its own accounting period
• Your company's accounting reference date (year-end) and any recent changes to it
• Whether you have a recent estimate of taxable profits for the current period
• Whether the company has associated companies or a director's loan account balance
• Whether you use an accountant or HMRC-recognised software to file the CT600

What you'll get

A personalised compliance report covering: a score out of 100, an executive summary, a list of findings ranked by severity, and a prioritised action plan with timeframes.