A limited company has several filing and payment deadlines that all hang off the accounting period end date, and the most common cause of penalties is mixing them up. The corporation tax payment is due before the corporation tax return. The accounts go to Companies House on a different timetable from the return that goes to HMRC. A separate confirmation statement is due once a year regardless of the accounts. Getting the calendar right is straightforward once the rules are clear, and it removes the most avoidable category of company penalties.
This spoke completes the corporation tax and year-end accounts hub. It assumes you already understand which rate applies, set out in the 25% main rate and 19% small profits rate spoke, and how to compute tax in the middle band, set out in the marginal relief calculation spoke. Here the focus is when everything is due and what happens if it is late.
The three core deadlines
For a private limited company with a standard twelve-month accounting period, three deadlines govern corporation tax and statutory reporting. The corporation tax payment is due 9 months and 1 day after the end of the accounting period. The CT600 corporation tax return is due 12 months after the end of the accounting period. The annual accounts are due at Companies House 9 months after the end of the accounting period. Notice that the payment falls due before the return, which catches out owners who assume tax is paid when the return is filed.
A worked calendar for a 31 March year-end
Concrete dates make the timetable easier to plan. Take a company with a 31 March accounting period end. The corporation tax payment is due 1 January the following year, being 9 months and 1 day after 31 March. The annual accounts are due at Companies House by 31 December, being 9 months after 31 March. The CT600 is due to HMRC by 31 March the following year, being 12 months after the period end. In practice most accountants prepare the accounts and the CT600 together well before the 31 December accounts deadline, so the tax figure is known in good time for the 1 January payment.
Why the payment comes before the return
The 9 months and 1 day payment deadline existing 3 months before the 12 month return deadline is deliberate. HMRC expects the tax to be calculated and paid before the formal return is filed, even though the return is the document that reports the figure. The practical consequence is that a company cannot leave everything until the return deadline. The numbers must be substantially worked out by the 9 months and 1 day point so the correct amount can be paid. Filing the return early, well before its 12 month deadline, is good practice precisely because it forces the calculation in time for the payment.
Quarterly instalments for large companies
The 9 months and 1 day rule applies to most owner-managed companies, but not to large companies. A company with taxable profits above £1.5 million pays corporation tax in quarterly instalments rather than in one lump after the year-end. A very large company, with profits above £20 million, pays on an accelerated instalment timetable. These thresholds are themselves divided among associated companies, so a group of several companies can fall into the instalment regime at lower individual profit levels. For the typical Harrow SME the single 9 months and 1 day payment applies, but growing companies should watch the £1.5 million threshold.
The first accounting period and its quirks
A company's first set of accounts is often the most confusing because the first accounting period rarely matches a clean twelve months. Companies House sets the first accounts filing deadline at 21 months after the date of incorporation, rather than 9 months after the period end, to allow for the longer first period. For corporation tax, where the first period of account exceeds twelve months, it is split into two accounting periods, the first twelve months and the balance, each with its own CT600 and its own payment date.
Two returns from one set of accounts
When a long first period is split, the company files one set of statutory accounts at Companies House covering the whole period, but two CT600 returns covering the two corporation tax accounting periods. The profit is apportioned between the two periods, usually on a time basis, and the rate limits are applied separately to each. This is a common source of confusion in a first year and is worth flagging to your accountant early.
The confirmation statement is separate
The confirmation statement is often confused with the annual accounts, but they are different filings with different purposes. The confirmation statement is a Companies House filing that confirms the company's registered details, directors, registered office, shareholders and people with significant control, are up to date. It is due at least once every twelve months and carries a filing fee. It is not a financial document and contains no profit or tax figures. A company can have nothing financial to report and still owe a confirmation statement.
Penalties for late filing and late payment
Each obligation carries its own penalty regime. Late annual accounts at Companies House trigger an automatic penalty that escalates with the delay, and the penalty doubles where accounts are late two years running. A late CT600 triggers HMRC penalties starting modestly and increasing with persistent lateness, with tax-geared penalties for prolonged delay. Late corporation tax payment attracts interest from the day after the payment deadline. The interest rate tracks the Bank of England base rate plus a margin, so on a sizeable tax bill even a few months of delay is a meaningful cost.
- Late accounts at Companies House: automatic penalty rising with the length of delay, doubled for a second consecutive late year.
- Late CT600: flat penalties for short delays, tax-geared penalties for prolonged delay.
- Late corporation tax payment: interest accrues daily from the day after the deadline.
- Late confirmation statement: the company and its officers can face penalties and the company risks being struck off.
How to keep the deadlines under control
- Record the accounting period end date and calculate all four deadlines from it at the start of each year.
- Diarise the 9 months and 1 day payment date as the binding one, since it falls first.
- Aim to finalise accounts and the CT600 before the 9 month accounts deadline, so the tax figure is settled in time to pay.
- Keep the confirmation statement date in a separate reminder, as it does not move with the accounts.
- Set aside corporation tax through the year so the payment is funded before it falls due.
A brief note on overdrawn director loans
One deadline-driven trap sits alongside corporation tax: the overdrawn director loan account. Where a director owes the company money at the year-end, a section 455 charge can arise if the loan is not repaid within 9 months and 1 day of the period end, the same date as the corporation tax payment deadline. Repaying the loan before that date avoids the charge. This is relevant here only because the deadline coincides with the main payment date, so it belongs on the same calendar; the detailed treatment of section 455 is a topic in its own right.
Changing your accounting reference date
A company can change its accounting reference date, which shifts the year-end and therefore every deadline that hangs off it. Shortening the period can be done more than once and brings the deadlines forward. Lengthening the period is more restricted: it can usually be done only once in five years and cannot take the period beyond eighteen months. Because every deadline recalculates from the new period end, any change should be planned with the filing and payment calendar in mind rather than made in isolation.
Frequently asked questions
When exactly is my corporation tax due?
For a company that is not large, corporation tax is due 9 months and 1 day after the end of the accounting period. For a 31 March period end that is 1 January. Large companies with profits above £1.5 million pay in quarterly instalments instead. The payment deadline falls three months before the deadline to file the CT600.
Are the HMRC and Companies House deadlines the same?
No. The annual accounts go to Companies House 9 months after the period end, while the CT600 goes to HMRC 12 months after the period end, and the tax payment to HMRC is due at 9 months and 1 day. They are three distinct dates, plus a separate confirmation statement due once every twelve months to Companies House.
What happens if I file my accounts late?
Companies House applies an automatic penalty that increases the later the accounts are filed, and the penalty doubles if accounts are filed late in two consecutive years. The penalty is charged regardless of whether the company owed any tax, so even a dormant or loss-making company should file on time.