Almost every tax deadline in the United Kingdom works the same way. You file the return and pay the tax on the same day. Self Assessment does it on 31 January. Value Added Tax does it a month and seven days after the quarter. It is a sensible arrangement, and Corporation Tax does not follow it.
Companies pay first and file three months later, and it is the payment date, not the filing date, that catches directors out, because nothing arrives to remind you of it. If your company’s year ended on 31 December 2025, your Corporation Tax is due on 1 October 2026, and your tax return is not due until the end of December. Here is why the gap exists and how to stay the right side of it.
The three dates, in the order they happen
For a private limited company with a 31 December 2025 year end, the calendar runs like this:
| What is due | When | The rule |
|---|---|---|
| Accounts to Companies House | 30 September 2026 | 9 months after the year end |
| Corporation Tax payment to HMRC | 1 October 2026 | 9 months and 1 day after the year end |
| Company Tax Return to HMRC | 31 December 2026 | 12 months after the year end |
Move the year end and everything moves with it. A 31 March 2026 year end means accounts by 31 December 2026, tax by 1 January 2027 and the return by 31 March 2027.
That extra day on the payment date is not a typo, and it is not a grace period either. It is simply how the legislation is written. The money is due nine months and one day after the year end, and interest starts the morning after that.
Why paying before you file is not as daft as it sounds
The obvious objection is that you cannot pay a bill you have not worked out yet. In practice you can, because the figure comes from your accounts rather than from the return.
Your accounts have to reach Companies House nine months after the year end, one day before the tax is due. If the accounts are done, the Corporation Tax number is done with them. The return is largely a matter of presenting that same figure to HMRC in the format it wants.
So the two deadlines only clash if the accounts are late, and a set of accounts that misses Companies House by a fortnight has usually missed the tax payment too. The dates are designed to be met together, and they tend to be missed together.
What being late actually costs
Interest on the tax. HMRC charges late payment interest at 7.75 per cent a year, calculated daily from the day after the due date until the money arrives. On £20,000 of Corporation Tax, a month late costs about £127 in interest. There is a small consolation: late payment interest on Corporation Tax is an allowable deduction, so the company gets tax relief on it. That softens the cost a little. It does not make being late a good idea.
Penalties on the return. These went up this year, and the increase applies to any Company Tax Return with a filing date on or after 1 April 2026, which means every 31 March 2025 year end onwards.
| How late the return is | Penalty |
|---|---|
| 1 day | £200 |
| 3 months | Another £200 |
| 6 months | 10 per cent of the unpaid tax |
| 12 months | A further 10 per cent of the unpaid tax |
If a company files late three times in a row, the two £200 penalties become £1,000 each. The old amounts were half this, so a firm that has been casually late for years is about to find it noticeably more expensive.
The fixed penalties apply even when the company owes no tax at all. A dormant company that forgets its return still gets the £200.
And at six months HMRC stops waiting. It raises what it calls a determination, its own estimate of what you owe, and that estimate cannot be appealed. You can only displace it by filing the actual return, by which point the percentage penalties are running.
The reward for being early, which nobody mentions
Pay your Corporation Tax before the due date and HMRC pays you interest on it, currently 3.50 per cent a year on early payments that are not due by instalments. It runs from the date you pay until the date the tax was actually due.
It is not a fortune, and the interest HMRC pays you is taxable income for the company, so the real return is lower than the headline. But if the money is sitting in a current account earning nothing, and the tax is definitely owed, paying it the moment the accounts are finished is tidier than watching it and better than forgetting it.
Getting the payment to land
Three practical things trip companies up on the day itself.
You cannot pay by post. Cheques to HMRC for Corporation Tax are no longer an option. Online or telephone banking, a debit or corporate credit card, Direct Debit or a payment at your bank.
Timing depends on the method. Faster Payments and card payments usually arrive the same day or the next. Bacs and a Direct Debit you have used before take three working days. A brand new Direct Debit takes five. If the deadline falls on a weekend or a bank holiday, the money has to be there on the last working day before, unless you are using Faster Payments.
The reference changes every year. Corporation Tax uses a seventeen character payment reference that belongs to one accounting period only. Reuse last year’s and the payment goes to the wrong period. This is one of the most common reasons companies receive a demand for tax they have already paid. The right reference is on your notice to deliver a return and in the company’s HMRC online account.
If the company owes nothing for the period, tell HMRC that rather than staying silent. A nil declaration takes a minute and stops the reminders and the estimates.
Which rate you are actually paying
For the financial year starting 1 April 2026 the rates are unchanged:
- 19 per cent on profits up to £50,000.
- 25 per cent on profits above £250,000.
- Between the two, the main rate applies with Marginal Relief, which produces an effective rate climbing from 19 per cent to 25 per cent.
If you control more than one company, those two limits are divided between them, so two associated companies each hit the 25 per cent rate at £125,000 rather than £250,000. Directors with a second company for a side venture are often surprised by this.
Paying in quarterly instalments only starts once profits run at more than £1.5 million a year, so for the overwhelming majority of owner managed companies there is one payment, once a year, nine months and one day after the year end.
One more thing that shares the date
If you have ever had an overdrawn loan from your own company, nine months and one day will already sound familiar. It is the same deadline for clearing a director’s loan account before the company picks up a Corporation Tax charge on the balance, now 35.75 per cent for loans made on or after 6 April 2026.
The two deadlines deliberately fall on the same day. If your year end was 31 December 2025, both the tax and the loan have to be sorted by 1 October 2026. The loan needs deciding well before then, because the cheapest ways to clear a balance take planning rather than a last minute bank transfer.
How our clients experience this
Mostly, they do not notice it. Accounts get prepared in the months after the year end rather than in the week before they are due, so the tax figure is known long before the money is needed, and we tell clients the number and the date as soon as we have both. The return goes in, the payment reference is the right one, and nobody discovers a deadline by receiving a penalty for missing it.
Ltd Company Starter is from £105 per month, and Growing Strong, for companies wanting more planning through the year, is from £205 per month. Both are fixed fees, with no charge for picking up the phone to ask when something is due.
If your year end has been and gone and you are not certain what you owe or when, Get your instant quote and see your fixed monthly fee in under a minute.