Your 'accounting period' for Corporation Tax is normally 12 months, and will usually be your company or association's financial year.
Your financial year is the time covered by your annual accounts.
Check your accounting period
Log in to the HM Revenue and Customs (HMRC) online Corporation Tax service to check the dates of your accounting period.
Your first accounting period
You'll get a letter from HMRC giving you dates for your accounting period after you start or restart your business.
Tell HMRC if you think the dates are wrong.
If your accounting period and financial year are different
Check what to do if your accounting period and financial year are different:
- in your first year of business
- when you restart your business
Your accounting period will end earlier than normal if your accounts cover less than 12 months, eg because:
- you close your business
- stop doing business temporarily
- shorten your financial year
You deal with your accounting period differently if your accounts cover more than 12 months - eg you've 'lengthened' your financial year.
If your accounts cover less than 12 months
Your accounting period should end on the same day as your accounts.
Log in to HMRC's online Corporation Tax service and follow the instructions to enter new dates for your accounting period before you prepare your Company Tax Return.
If you use accounting software to send your return, enter the new dates for your accounting period before you send your return.
If your accounts cover more than 12 months
Your accounting period can't be longer than 12 months.
If you were trading continuously, you'll have 2 accounting periods - one for 12 months and one for the rest of the time.
If you weren't trading continuously, you start a new accounting period each time your business situation changed - eg on the date you stopped or started trading, or began winding up your business.
You must file a Company Tax Return for each accounting period - enter new dates for each period before you prepare each return.
Include your accounts with the first return only.
Explain why you're not including accounts with the other returns - how you do this depends on whether you use HMRC's online Corporation Tax service or accounting software.