SimpleReturns

What happens after you hit submit?

Updated 31 July 2026
The short answer

You should get two confirmations, not one: HMRC confirms it has your tax return, and Companies House confirms it has your accounts. Both mean received and passed the checks, not "HMRC agrees your figures". After that, three dates matter: pay the tax by 9 months and 1 day after your year end, keep your records for six years from the end of the last company financial year they relate to, and HMRC normally has 12 months from the day you filed to ask questions.

Official source. This guide is a plain-English summary of official GOV.UK guidance, not advice. The authoritative source is Company Tax Return obligations on gov.uk. Always rely on that over our summary.

Did it actually work?

If your return was accepted, HMRC sends back a receipt with a unique reference on it. Save it. That reference is your proof of what you sent and the date you sent it, and it's the thing to quote if anyone ever asks whether you filed.

An acceptance means two things and only two things: HMRC has your return, and it got through the automatic checks its system runs before taking a submission. It does not mean HMRC has looked at your numbers and agreed them. The receipt is produced automatically, so treat it as proof of delivery, never as a verdict on your figures.

If instead you got a rejection, that's a different situation with its own short list of causes, and HMRC rejected your CT600 walks through each one.

Why am I waiting for two confirmations?

Your accounts and your tax return go to two different places. The accounts go to Companies House, which keeps the public record of your company. The tax return goes to HMRC, which handles the tax. Two organisations, two systems, two answers. (Companies House vs HMRC covers who does what.)

Companies House usually sends you two emails of its own: one to say your accounts arrived, and a second to say they've been accepted. The second one often lands within a working day, sometimes up to three. Wait for that second email before you count the accounts as done. If your deadline is close and the accounts come back rejected, you don't get extra time to fix them.

I've filed. Have I paid?

No. Filing tells HMRC what you owe. Paying is a separate job, and it comes first.

Your Corporation Tax is due 9 months and 1 day after the end of your accounting period. Your return is due 12 months after the end of that period. So the money is due almost three months before the paperwork, which catches out a lot of people who assume the two deadlines are the same day.

A quick example. Your company's year ends on 31 March 2026, and the tax works out at £4,750:

  • £4,750 due by 1 January 2027 (9 months and 1 day after 31 March 2026)
  • Return due by 31 March 2027 (12 months after 31 March 2026)

File in October, and the £4,750 still has to reach HMRC by that same January date. Filing early is fine and doesn't move the payment date.

For example

One catch worth knowing, because this example runs straight into it: 1 January 2027 is a bank holiday. When your payment date lands on a weekend or a bank holiday, the money has to reach HMRC on the last working day before it, which here is Thursday 31 December 2026. The exception is paying by online or telephone banking, which arrives the same day.

How to pay your Corporation Tax bill has the methods, the timings, and the reference number to use, which isn't the one you might expect.

What do I need to keep, and for how long?

Keep your records for six years from the end of the last company financial year they relate to. Not six years from the day you filed, and not six years from the date on the receipt. So records for a year ending 31 March 2026 are kept until 31 March 2032.

You keep them longer in a few cases: a purchase you expect to use for more than six years, like a van or machinery; a transaction that spans more than one accounting year; a return you filed late; or a return HMRC has started checking.

Records means the everyday evidence: bank statements, sales invoices, purchase receipts, and anything showing what the money was for. What records do I need to keep? lists them properly.

How long can HMRC come back to me?

For a return filed on time, HMRC normally has 12 months from the day you filed it to open a formal check. Note the start point: it runs from the date you sent it, not from the deadline. File eight months early, and your quiet period starts eight months earlier too.

That window stretches in a few situations. Filing late pushes it out. So does amending the return, which opens a fresh window on the changed figures. And where a mistake was careless or deliberate rather than honest, HMRC can look back a great deal further than a year.

Separately, HMRC can tidy up an obvious slip in your return without any of this being a check on you.

Most companies hear nothing at all. If you want to know what a check actually involves, what happens if HMRC checks your Corporation Tax covers it.

What if I spot a mistake now?

You can change it. You normally have 12 months from the filing deadline to amend a Company Tax Return, which for a normal 12-month year is roughly two years after your year end. You resend corrected figures and HMRC squares up the difference, either you owe a bit more or you get some back.

The window runs from the deadline, not from the day you filed, so filing early gives you longer to spot something. How to amend your Company Tax Return has the steps and what to do if you're outside the window.

How SimpleReturns handles it

We send both parts, the accounts to Companies House and the tax return to HMRC, and show you each confirmation as it comes back, with the reference. Your figures, your accounts and your submitted return stay in your account to download, so the records side of the six-year rule doesn't depend on you finding an old email.

Common questions

Does an accepted return mean HMRC agrees with my figures?

No. It means HMRC has your return and it passed the automatic checks. Agreeing your figures is a separate thing that hasn't happened, and for most companies never needs to.

Why haven't I heard from Companies House yet?

Their acceptance email is usually within a working day and can take up to three. You should get one email confirming they received your accounts and a second confirming they've accepted them.

I've filed. Does that mean I've paid?

No. The tax is due 9 months and 1 day after your year end, three months before the return itself is due.

How long do I keep my paperwork?

Six years from the end of the last company financial year it relates to. Longer if you filed late, if HMRC is checking the return, if you bought something you expect to last more than six years, or if a record covers more than one accounting period.

How long can HMRC ask questions about this return?

Normally 12 months from the day you filed it. Filing late or amending the return extends that, and a careless or deliberate error can be looked at much later.

Can I still fix a mistake after filing?

Yes, normally up to 12 months after the filing deadline. You send corrected figures and HMRC adjusts the tax.

Ready to do it the easy way?

We prepare your accounts and your tax return, send both, and show you every figure before anything leaves your screen, for £99, once, no subscription. When each confirmation arrives, you'll see it, so you're not left guessing whether it worked.

Start your return

If your company is more complex, like a group, or you already know HMRC is checking a past year, an accountant may be the better fit, and that's an honest call to make.

General guidance, not advice. This guide explains how the rules generally work for small UK limited companies. It isn't tax advice for your specific situation, if you're unsure, check with us or an accountant.