A first year trading can be longer than twelve months, if needed to align with an accounting cycle. This is known as an 'Extended Accounting Period'. Whilst this makes perfect sense to take advantage of an extended period for reporting, when you need to file your CT600 Corporation Tax return you need to make two separate Company Tax CT600 Filings, as a single CT600 return can't be longer than 12 months.
You can either create the first CT600 and accounts using the QuickStart dialog which after selecting your company, Accounting period start date and company size (Micro or Small) - or alternatively create 2 CT600 filings and IXBRL accounts separately.
In both cases you should end up with 3 Filings in your blotter which will hopefully look like the below:
In this example the accounting year has been extended to cover the period 1st of June 2018 to 31st of December 2019. (19 months)
Note that the first CT600 accounting period starts on the 1st June 2018 and ends on the 31st May 2019 (12 months). The second CT600 starts on the 1st June 2019 and ends on the 31 December 2019 (7 months).
The IXBRL accounts can cover the entire extended accounting period (in our example 1st of June 2019 to 31st of December 2019.) - which makes the filing slightly easier.
The primary question here is normally "what to enter for turnover in CT600 when
accounting year is more than 12 months"?
It's up to you to decide how your attribute your turnover and income across the 2 periods - however generally your records / accounting system should be able to provide what income and expenditure you had for each.
When you are completing the CT600, in the declaration section you will need to allocate the IXBRL accounts that you have created. Note that Box 80 is set to YES; Box 85 is set to NO, and; Box 90 is set to Not applicable. With box 91A being set to the IXBRL Company Accounts. Note: if you have supplied your own IXBRL accounts you can select to upload them in the dropdown menu in box 91A.
Note: Although in this example we had the longer period (the 12 month period) first, it actually makes no difference and therefore you could have the shorter period for the first CT600.
Once you have completed your returns and completed the above you will now be able to submit, you can submit in any order, normally though the CT600 return with the accounts attached is sent first - as if you get rejection errors it better to deal with those first. Once you have submitted both (and hopefully accepted), you will receive emails from EasyDigitalFiling with your IRMark (digital hash) and later (possibly 4-12 hours) an email from HMRC.
All done - at this stage you will feel like a master. The pressure is off, for another year anyway!