Taxfiler Important Known Issues

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

Issues resolved in the 2023.5.2 release

Corporation Tax – CT600 Version 3

HMRC issued a revised version of the CT600 to accommodate the main rate of corporation tax of 25% and reporting of marginal relief calculations.

In addition, there were changes to the rates of tax credit both for SME Research and Development tax credit and the Research and Development Expenditure Credit (RDEC) that come into effect from 01/04/2023. 

It is now possible to calculate the correct tax credit for research and development expenditure incurred from 1/4/2023 in respect of accounting periods that straddle 1/4/2023.

In addition, you can now submit a CT600 where the accounting period ends after 1/4/2023 and profits are chargeable to tax at the main rate of 25%.

Outstanding issues

Individuals – Capital Gains

Taxfiler does not currently automatically charge the correct amount of capital gains tax in respect of disposals with proceeds in excess of £1 million that qualify for Business Asset Disposal Relief (BADR).

It is necessary to split the disposal record into two such that one is up to £1 million and the balance a separate record on which no BADR is claimed. 

This issue will be resolved in a future release.


The 2023 questionnaire does not include the address details in respect of income from property.

This issue will be resolved in a future release.

Individuals – calculation

The SA100 calculation was missing the Total income Tax due section at the foot of the calculation report.

This issue will be resolved in a future release.