An accounting period is the period a single Company Tax Return covers for Corporation Tax. It usually matches the company's financial year, but it can never be longer than 12 months.
When it starts and ends
A company’s first accounting period starts when it comes within the charge to Corporation Tax, usually when it starts to trade or first has a source of income. After that, each period starts the day after the last one ended. A period ends on the earliest of:
- 12 months after it started;
- the date the company’s accounts are made up to;
- the company starting or ceasing to trade, or going into liquidation.
When the accounts cover more than 12 months
If a set of accounts covers more than 12 months, which often happens with a company’s first accounts, it is split into two accounting periods: the first 12 months, then the remainder. Each has its own CT600, its own payment date and its own filing deadline.
Heads up — the accounting period is not the same thing as the financial year for Corporation Tax, which runs from 1 April to 31 March and is what the tax rates are set for.
Read more: Creating a Corporation Tax accounting period and Long periods of account.