Dates set by your year end
Accounts to Companies House: 9 months after your accounting year end. (For your first ever accounts, the deadline is 21 months after incorporation.)
Corporation Tax payment to HMRC: 9 months and one day after the end of your accounting period.
Company Tax Return (CT600) to HMRC: 12 months after the end of your accounting period.
The confirmation statement
Separately from accounts, every company must file a confirmation statement with Companies House at least once every 12 months — it confirms details such as directors, shareholders and the registered office.
It is due within 14 days of the end of your review period, and it applies to every company, including dormant ones.
Other dates, if they apply to you
If the company is VAT registered, VAT returns follow their own cycle — typically quarterly under Making Tax Digital.
If the company runs payroll, PAYE and National Insurance are reported each pay run and paid to HMRC monthly or quarterly.
These sit outside OneFiler’s scope, but they belong on the same calendar if they apply to your company.
A practical approach
Put three reminders in your diary as soon as your year end passes: accounts and tax payment at the 8-month mark (to leave margin), and the tax return well before the 12-month mark.
Better still, file everything together shortly after your year end — OneFiler submits the accounts and the tax return in one process, which clears the whole calendar at once.