Your first company year end has two separate clocks: Companies House wants the first accounts by the first-accounts deadline, and HMRC may split the first Corporation Tax period because a tax accounting period cannot run for more than 12 months. For a founder, the job is to keep records clean from the start, put aside the cash you'll need to pay the tax, and check if your first period runs longer than a year.
What is different about a first company year end?
After incorporation, Companies House sets an accounting reference date. Your first accounts usually cover the period from incorporation to that date. Later accounts usually cover a standard financial year.
HMRC uses Corporation Tax accounting periods, and a Corporation Tax accounting period cannot exceed 12 months. That means your first set of accounts can cover one period for Companies House, while HMRC needs two Company Tax Returns if the accounts cover more than 12 months.
The founder consequence is cash timing. A long first accounts period can create one Companies House accounts filing, two CT600s, and two Corporation Tax payment dates. A quirk of the UK tax system is that the payment can fall due before the tax return is even filed.
When are first accounts due at Companies House?
For a private company, first accounts are due 21 months after incorporation. After the first accounts, the normal private-company accounts deadline is 9 months after the financial year end.
Companies House treats the deadline as met only when acceptable accounts are received. A rejected filing counts as not delivered. Weekends and bank holidays do not extend the deadline. Leave time for review, signatures and any rejection rather than treating the due date as the day to start.
You can check the current deadlines on GOV.UK's annual accounts deadlines page.
Why can a first year need two CT600s?
HMRC does not let a Corporation Tax accounting period run for more than 12 months. If your first accounts cover more than 12 months, HMRC splits the period into a 12-month accounting period and a short second accounting period.
That creates two CT600s: one for each Corporation Tax accounting period. For a first period of account of 18 months or less, both returns share one filing deadline: 12 months after the end of the period of account.
The Company Tax Return normally includes the CT600, the company accounts and the Corporation Tax computations. GOV.UK's Company Tax Returns guidance is the public source for the return.
When is Corporation Tax paid in the first year?
For most founders, your company's Corporation Tax is due 9 months + 1 day after the end of the accounting period. If HMRC splits the first year into two accounting periods, there can be two payment dates.
That timing matters because the payment date can arrive before the CT600 filing date. A separate tax pot keeps the cash available while the accounts and tax return are being finalised. Our guide on profit, cash and the tax pot explains the habit.
What records should be ready before the first year end?
The first year is where the bookkeeping routine gets tested. Have these ready before the accounts work starts:
- bank statements and bookkeeping access from incorporation
- sales invoices, platform reports and customer balances
- supplier bills, subscriptions and receipts
- payroll records and any PAYE submissions
- dividends, board minutes and dividend vouchers
- director's loan account movements
- loan, grant, funding or share-issue paperwork
- asset purchases and finance agreements
- VAT returns and VAT control account, if registered
- stock, work in progress or deferred revenue where relevant
This list is broader than the final accounts because the accounts are only as good as the records behind them. Clean first-year records also make the second year easier: the tax calendar, bookkeeping routine and founder-pay decisions start from better data.
What should a new founder decide after the first accounts?
Use the first accounts to set the routine for the next year. Check whether the salary/dividend pattern still makes sense, whether the director's loan account needs tighter review, whether VAT needs monthly monitoring, and whether the tax pot is being funded at the right pace.
The related Carr guides to line up next are how to pay yourself from a limited company, director's loan account s455, VAT registration threshold, and the wider limited company year-end checklist.
Frequently asked questions
What is a first company year end? It is the first date your company accounts are made up to after incorporation. The first accounts usually run from incorporation to the first accounting reference date set by Companies House.
When are first company accounts due? For a private company, first accounts are due 21 months after incorporation, or 3 months after the accounting reference date if that is longer. After the first set, private-company accounts are normally due 9 months after the financial year end.
Can a first year need two CT600s? Yes. If the first accounts cover more than 12 months, HMRC splits the period into Corporation Tax accounting periods because one accounting period cannot exceed 12 months. That can mean two CT600s for one first set of accounts and two payment dates.
When is Corporation Tax due in the first year? For companies outside quarterly instalment payments, Corporation Tax is due 9 months + 1 day after each Corporation Tax accounting period ends. A long first accounts period can therefore create two payment dates.
Are Companies House and HMRC deadlines the same? The deadlines run separately. First accounts are due to Companies House 21 months after incorporation, while CT600 filing and Corporation Tax payment follow HMRC's accounting-period rules.
Work with us
If your first company year end is coming up and you want the records, dates and tax cash checked before the rush, book a call with Carr Accounting Studio. We will help you get the first cycle clean so the second one is easier.
General information, not advice. UK figures current to 2026/27 — check the latest before you rely on them. Written by David Carr, chartered accountant and founder of Carr Accounting Studio.