Initially, when purchasing in April, the Ftax CT600 will allow tax filing for accounting periods up to the March 31st just preceding that tax year.
HMRC usually update their CT600 tax filing requirements during September/October.
The Ftax CT600 will then be updated to allow tax filing for accounting periods up to the March 31st at the end of that tax year.
This upgrade is free so long as the tax year Ftax CT600 credits have been purchased.
The Ftax form itself will clearly state the latest accounting period end date that may be submitted using that form version.