Apologies if this has been posted already. I tried to submit a CT600 for a company whose period ended on 30/04/2020 and received an error :"The period to which this Return's Computation applies does not coincide with the effective from/to dates of the referenced Computation Taxonomy. Please correct and re-submit." This means that any calculation for this period using the correct 19% Corporation Tax rate will be rejected.
Taxfiler support have informed me that no CT600 returns that cover accounting periods that end on or after 01/04/2020 can be filed at present - I am not sure if the issue persists for other software but presume so. HMRC have indicated that their fix will not be in place until the second week of July 2020.