What are the deadlines, in one list?
Everything counts from the day your company's financial year ends (your "year-end"). You have three jobs, and two of them go to two different places:
- Pay your Corporation Tax to HMRC: 9 months and 1 day after your year-end.
- Send your tax return to HMRC: within 12 months of your year-end.
- Send your accounts to Companies House: within 9 months of your year-end.
HMRC and Companies House are two separate government bodies. Your tax return goes to HMRC. Your accounts go to Companies House. They are two filings to two places, even though most of the numbers come from the same year.
Wait, I pay the tax before I send the tax return?
Yes, and this trips a lot of people up. The deadline to pay comes about three months before the deadline to file your tax return.
So you work out what you owe, pay it by 9 months and 1 day, and you still have a few more months before the tax return itself has to be in. In practice most small companies do it all in one go, well before the pay date, so they know the figure and pay on time. The point to remember: paying and filing are two different deadlines, and paying comes first.
A real example with dates
Say your company's year ends on 31 March 2026. Here is exactly when each thing is due:
| What you do | Who it goes to | Deadline | The date |
|---|---|---|---|
| Pay your Corporation Tax | HMRC | 9 months and 1 day after year-end | 1 January 2027 |
| Send your tax return | HMRC | 12 months after year-end | 31 March 2027 |
| Send your accounts | Companies House | 9 months after year-end | 31 December 2026 |
So for a 31 March year-end, your accounts are due first (end of December), then your tax payment a day later (start of January), then your tax return last (end of March). Different year-end, different dates, but always the same gaps.
(Your first year is the odd one out. Your very first accounts are due 21 months after the day your company was set up, not 9 months, because that first period is longer. We cover the first-year dates on their own page.)
What happens if I file my tax return late to HMRC?
HMRC charges a fine the moment you miss the tax-return deadline, and it grows the longer you leave it. The fixed fines are:
- 1 day late: £200.
- 3 months late: another £200, so £400 in total.
- 6 months late: HMRC works out the tax bill for you and adds 10% of the tax you still owe on top.
- 12 months late: another 10% of the tax you still owe.
If your company files its tax return late three years running, those £200 fines jump to £1,000 each. And the fixed fines apply even if your company owes no tax at all, as long as HMRC was expecting a return.
What happens if I file my accounts late to Companies House?
This is a separate fine from a separate body, on top of anything HMRC charges. Companies House fines a private company by how late the accounts are:
- Up to 1 month late: £150.
- 1 to 3 months late: £375.
- 3 to 6 months late: £750.
- More than 6 months late: £1,500.
If your accounts are late two years in a row, Companies House doubles the fine. So missing both your HMRC return and your Companies House accounts means two sets of fines, not one.
How do I make sure I never miss one?
The honest answer is to write all three dates down the moment you know your year-end, and aim to do everything a month or two early. Doing it early means you know your tax figure in good time and you are never near a deadline.
If you would rather not track three dates by hand, our deadline checker works out your exact dates from your year-end in a few seconds, and when you file with us, your tax return and your accounts go in together so you are not juggling two filings.
How SimpleReturns handles it
Tell us your year-end and we show you all three dates and how long you have. When you file, we send your tax return to HMRC and your accounts to Companies House in one guided run, so you do not have to remember which goes where. You only pay the tax to HMRC yourself, using their payment reference, by the pay deadline we show you.