Filing your company accounts and CT600 yourself

Step by step

1. 1Find your accounting period end and deadlines: accounts are due at Companies House 9 months after the year end (21 months after incorporation for your first accounts), Corporation Tax is due 9 months and 1 day after, and the CT600 12 months after
2. 2Get your company authentication code from Companies House and your Corporation Tax UTR from HMRC (keep both private, never enter them on CleverTax)
3. 3Bring your books up to date here: income, expenses, director's salary and director's loan balance, then check your Corporation Tax estimate
4. 4Prepare your annual accounts. Most small companies can use micro-entity accounts. Companies House WebFiling for accounts closes on 31 March 2028. From 1 April 2028 all accounts must be filed using software
5. 5File your accounts with Companies House before the deadline
6. 6Choose HMRC-recognised software that can produce and submit a CT600, a tax computation and iXBRL accounts (GOV.UK keeps the list)
7. 7Enter your figures, check them carefully and submit your CT600 to HMRC
8. 8Pay your Corporation Tax by 9 months and 1 day after the year end, even though the return is due later

Common mistakes

• Thinking filing with Companies House also covers HMRC (it doesn't, you file both)
• Paying Corporation Tax at the 12-month return deadline instead of 9 months and 1 day
• Forgetting to file because the company made a loss or didn't trade
• Leaving it too late to find software, as HMRC's free filing service has closed

Related guides

• Corporation Tax marginal relief
• Director's loan account s455
• Paying yourself from a company