Last reviewed: 29 September 2026 · Reviewed by IFM's qualified accountant
The two deadlines are related but legally distinct. A payment made on time does not excuse a late return, and a return filed on time does not prevent interest where the tax reached HMRC late.
Which period controls the deadlines?
Corporation Tax runs by accounting period. The period is usually the same as the company’s financial year, but not always. It can differ in the first year, after a dormant company starts trading, when a company stops trading, or when the Companies House year end changes.
A Corporation Tax accounting period cannot be longer than 12 months. If statutory accounts cover more than 12 months, the company normally files two Company Tax Returns: one for the first 12 months and another for the remaining period. Each return has its own filing date, and the tax for each period has its own payment date.
HMRC sends accounting-period dates after Corporation Tax services are added to the business tax account. Check those dates against the actual trading start and the statutory accounts. If the company lengthens its financial year, GOV.UK says it must update its accounting periods with HMRC before the original filing date.
What should you know about the standard payment deadline?
A company with taxable profits of up to £1.5 million normally pays nine months and one day after the end of its accounting period. A period ending 31 March would therefore normally have a payment date of 1 January in the following calendar year.
The money must reach HMRC by the deadline. Payment methods take different lengths of time. GOV.UK lists same-day or next-day methods, including Faster Payments and approved online card or bank-account routes, while Bacs and Direct Debit can take longer. A first Direct Debit can require five working days.
Where the due date falls on a weekend or bank holiday, make sure cleared funds reach HMRC on the last working day before it. GOV.UK gives an exception for Faster Payments using online or telephone banking, but it remains sensible to avoid leaving a material payment to the last day.
Use the 17-character Corporation Tax payment reference for the correct accounting period. The reference can be found in the company’s online account or on its notice to deliver. A payment with the wrong reference may be allocated to a different bill and appear unpaid against the intended period.
When instalment payments apply?
Companies with taxable profits above £1.5 million normally pay Corporation Tax by quarterly instalments. Separate rules apply above £20 million. These thresholds can be reduced according to the number of associated companies, and a period shorter than 12 months can also affect the calculation.
This means £1.5 million is not a safe stand-alone test for a company in a group or under common control. If profits are approaching the threshold, check the instalment rules before relying on the nine-month-and-one-day date. Instalment payments can begin before the accounting period ends.
What should you know about the return filing deadline?
The Company Tax Return is normally due 12 months after the end of the accounting period. A return includes the company tax computation and accounts in the required format, together with the CT600 information.
HMRC requires a return when it issues a notice to deliver one. The obligation can remain even if the company made a loss or believes no Corporation Tax is payable. A dormant company that has received a notice may need to file for that period before HMRC stops requiring later returns.
The later filing date is useful for finalising disclosure, but it is not a reason to postpone the core calculation. The amount due has already reached its normal payment date three months earlier.
What should you know about late payment consequences?
HMRC charges late payment interest from the due date until the tax is paid. The rate can change, so check the current GOV.UK interest-rate table rather than copying an old percentage into a permanent calendar.
If cash is tight, contact HMRC rather than simply missing the date. A Time to Pay arrangement depends on the circumstances and is not automatic. Continue preparing the return and establish the amount as accurately as possible; uncertainty about the final filing does not stop interest accruing on unpaid tax.
Paying too early can also have a consequence: HMRC may pay credit interest, subject to its rules and current rate. The main planning point is not to optimise a few days of interest, but to use the right reference and ensure the payment clears.
If the final calculation changes an estimate already paid, deal with the difference promptly. Pay an underpayment with the correct period reference and check the interest position. Where the company has overpaid, the amount may be available against another liability or for repayment through HMRC’s processes. Do not reduce an unrelated payment informally and assume the accounts will net off: check how HMRC has allocated each amount in the business tax account.
What should you know about late return penalties from April 2026?
The fixed penalties doubled for returns with filing dates on or after 1 April 2026. The current GOV.UK schedule starts with:
- £200 when the return is late;
- another £200 when it becomes more than three months late;
- 10% of unpaid tax at the tax-related penalty point; and
- another 10% later if the return remains outstanding.
HMRC’s detailed determination notes explain that repeated late returns can increase the fixed amounts to £1,000 and £2,000 for the third and successive consecutive failures. Tax-related penalties depend on the amount unpaid and the length of the delay.
HMRC can issue a tax determination when a return is substantially overdue. The company cannot appeal the determination itself; it needs to file the return so HMRC can replace the estimate with the proper calculation. A late filing appeal normally requires a reasonable excuse, and the return must be filed before the company appeals the penalty.
Why accounts, payment and filing should be one process?
The cleanest timetable begins soon after the period end. Reconcile the bookkeeping and tax control accounts, agree year-end adjustments, identify disallowable expenses and reliefs, and calculate a reliable tax provision. Approve the payment several working days before it is due.
Then complete and review the statutory accounts and Company Tax Return together. Although their recipients and deadlines differ, the figures must be consistent. Resolve differences deliberately, such as tax adjustments or periods split across two returns, rather than allowing them to appear as unexplained mismatches.
Record the Companies House accounts deadline separately. A common small-company sequence is payment at nine months and one day, Companies House accounts at nine months, and the Company Tax Return at 12 months, but the reference periods are not necessarily identical. First accounts and changed year ends need particular care.
What should you know about a simple deadline check?
For each Corporation Tax accounting period, keep five fields:
- period start and end;
- expected taxable profit and whether instalments might apply;
- payment due date and correct payment reference;
- Company Tax Return filing date; and
- Companies House accounts period and filing date.
Use the Deadline Finder for standard first accounts, first confirmation statement and Corporation Tax dates. For VAT, payroll, personal tax and other obligations, check the tax deadlines calendar and your official records.
What should you read next?
Use the Deadline Finder for standard first accounts, first confirmation statement and Corporation Tax dates. For VAT, payroll, personal tax and other obligations, check the tax deadlines calendar and your official records.
What do people also ask about this topic?
Which period controls the deadlines?
Corporation Tax runs by accounting period. The period is usually the same as the company’s financial year, but not always. It can differ in the first year, after a dormant company starts trading, when a company stops trading, or when the Companies House year end changes.
What should you know about the standard payment deadline?
A company with taxable profits of up to £1. 5 million normally pays nine months and one day after the end of its accounting period. A period ending 31 March would therefore normally have a payment date of 1 January in the following calendar year.
When instalment payments apply?
Companies with taxable profits above £1. 5 million normally pay Corporation Tax by quarterly instalments. Separate rules apply above £20 million. These thresholds can be reduced according to the number of associated companies, and a period shorter than 12 months can also affect the calculation.
What should you know about the return filing deadline?
The Company Tax Return is normally due 12 months after the end of the accounting period. A return includes the company tax computation and accounts in the required format, together with the CT600 information.
Which official sources support this guide?
- https://www.gov.uk/pay-corporation-tax
- https://www.gov.uk/company-tax-returns
- https://www.gov.uk/prepare-file-annual-accounts-for-limited-company
General guidance, not advice for your situation.
