First accounts and first Corporation Tax deadlines for a new UK limited company
A new private limited company's first accounts usually cover more than 12 months, and they are due at Companies House 21 months after incorporation or 3 months after the accounting reference date, whichever is longer. Corporation Tax works differently because an accounting period cannot be longer than 12 months, so you may file 2 tax returns for your first accounts, each with its own tax payment due 9 months and 1 day after its period ends, while both CT600s are normally due on the same day, 12 months after the end of the first accounts period.
Figures checked on GOV.UK on 24 October 2026
The figures
| Item | Rule | Source |
|---|---|---|
| First accounts start | The day the company was incorporated | GOV.UK |
| First accounts end | The accounting reference date (ARD) Companies House sets for the end of your financial year (GOV.UK example: set up 11 May, ARD 31 May the following year) | GOV.UK |
| First accounts deadline (if they cover more than 12 months) | 21 months from incorporation or 3 months from the ARD, whichever is longer | Companies House |
| Later accounts deadline | 9 months after the ARD | Companies House |
| Corporation Tax accounting period | Cannot be longer than 12 months | GOV.UK |
| Number of CT600s for the first accounts | Often 2, with 2 payment deadlines | GOV.UK |
| Corporation Tax payment (profits up to £1.5m) | 9 months and 1 day after the end of each accounting period | GOV.UK |
| CT600 filing deadline | 12 months after the end of the period of account, so when the first accounts run longer than 12 months (up to 18), both returns are normally due on the same day | HMRC |
| Profits over £1.5m | Pay by instalments instead | GOV.UK |
A worked example
This is GOV.UK's example with the deadlines added. A company is set up and starts trading on 11 May 2024, and Companies House sets its accounting reference date as 31 May 2025, so the first accounts cover 11 May 2024 to 31 May 2025, which is 12 months and 3 weeks.
| What | Period | Deadline |
|---|---|---|
| Companies House first accounts | 11 May 2024 to 31 May 2025 | 11 February 2026 (21 months from incorporation, which is later than 31 August 2025, 3 months after the ARD) |
| Corporation Tax payment, period 1 | 11 May 2024 to 10 May 2025 | 11 February 2026 |
| Corporation Tax payment, period 2 | 11 May 2025 to 31 May 2025 | 1 March 2026 |
| CT600, period 1 | 11 May 2024 to 10 May 2025 | 31 May 2026 |
| CT600, period 2 | 11 May 2025 to 31 May 2025 | 31 May 2026 |
The payment dates come from the GOV.UK example. Both CT600s are due 12 months after the end of the period of account, 31 May 2025, because HMRC's rule in CTM93030 dates every return from the end of a period of account that is no longer than 18 months, even though the tax for period 1 is paid earlier. After this first cycle, accounts and tax returns normally line up with the company's financial year, 1 June to 31 May.
The trap is that the tax is due about three months before the return that calculates it, so waiting until the CT600 is ready before paying usually means paying late, and HMRC may charge interest.
Frequently asked questions
When are my first accounts due at Companies House?
If your first accounts cover more than 12 months, which most do, they are due 21 months after incorporation or 3 months after your accounting reference date, whichever is longer. After that, a private company has 9 months from the end of each financial year.
Why might I have to file 2 Corporation Tax returns in my first year?
A Corporation Tax accounting period cannot be longer than 12 months, but your first accounts usually run for more than 12 months. So HMRC often needs one return for the first 12 months and a second return for the rest of the period, each with its own payment date, although both returns are normally due on the same day, 12 months after the first accounts period ends.
Is Corporation Tax due on the same date as my CT600?
No, the money comes first. For companies with taxable profits up to £1.5 million, the tax is due 9 months and 1 day after the end of the accounting period, while the CT600 is due 12 months after the end of the period of account, which is the period your accounts cover.
What if my company did not start trading straight away?
A company can be dormant for Corporation Tax between incorporation and starting to trade. What you file then depends on whether you added Corporation Tax services to your business tax account before your accounting reference date, so check the GOV.UK first accounts guide for your case and the notice to deliver a Company Tax Return you receive.
Do I need to keep books from day one, even before my first year end?
Yes, a limited company must keep accounting records from incorporation, covering money coming in and going out, what the company owns and what it owes, and those records are what your first accounts and tax returns are built from.
Your first accounts and CT600s filed - without working out two sets of dates yourself
Absolv's flat monthly fee includes year-end accounts and the CT600, with your books live in ten working days or your first month free, and if we're late, we pay the penalty. The filing deadlines tool adds your company's real Companies House and HMRC dates to your calendar, and this guide covers the move from freelancer to limited company.
Sources
- GOV.UK, your limited company's first accounts and Company Tax Return
- GOV.UK, first accounts: you started trading after your company set up
- Companies House, late filing penalties
- GOV.UK, pay your Corporation Tax bill
- GOV.UK, Company Tax Returns
- HMRC Company Taxation Manual, CTM93030: filing date for a return
- HMRC, Company Tax Return obligations
- GOV.UK, running a limited company: company and accounting records
Checked on 24 October 2026. Thresholds, deadlines and penalties change, so check the GOV.UK page before you rely on a figure.