IRIS Important Known Issues

It is important to us that we resolve any problems that are found in the IRIS Accountancy Suite.

If your problem is listed below, we are working hard to resolve these as quickly as possible.
Issues that have been fixed or are due to be fixed in the next release, are identified as such.
For information on the next release dates, click here.

Outstanding issues

IRIS Business Tax

Multiple Trade Losses Brought Forward for Extended Period Incorrect 
Where a business has multiple trades and has an extended accounting period, the losses brought forward are incorrect for the 2nd CTAP.
Workaround 
There is no workaround for this issue.
This issue is due to be resolved in the Summer 2026 release.

CT600 – Box 650 not completed for RDEC claims
When filing a CT600 for a small or medium-sized company with an RDEC claim, Box 650 is not being automatically populated. If Box 657 has also been completed, this triggers an online filing error.
Workaround
There is no workaround available for this issue.
This issue is due to be resolved in the Spring 2026 service pack release.