Companies must file accounts once a year at Companies House. Statutory abbreviated accounts must be filed at Companies House 9 months after your year-end date (6 months if a Plc).
For small companies, an abbreviated set of accounts can be filed, whereas medium and large companies must file a full set of accounts. A full set of accounts must also be submitted with HMRC along with a CT600.
An abbreviated set of accounts show a simplified Balance Sheet and a summary set of notes to the accounts with no need to submit a detailed profit and loss account showing turnover, cost of sales, overheads etc.
Full accounts will show a more detailed set of notes and will contain a detailed profit and loss account, meaning more of your information can be accessed.
HMRC also require a set of accounts along with a Corporation Tax calculation on a CT600 form to ensure the correct amount of tax is paid by the company on its profits.