3320 - The period to which this returns computation does not coincide with the effective from/to dates of the referenced computation Taxonomy. Please correct and submit.

HMRC implemented a change to the Corporation tax system on 11/12/17. This change relates to their system being unable to accept certain tagging standards for accounting periods starting after 31/12/2015. This is the tagging that is applied within the computations. 

This means that returns submitted after the 11/12/2017 for accounting periods starting on 01/01/2016 or after, should include the updated tagging requirements. If they do not, you will be presented with this error message. As long as you are running version 6.1.031 or higher, you should not encounter this message upon re-submission. Please see the link to our Knowledge Base article for information on How do I update TaxCalc to the latest version? (Practice users).