IAS23043 Business Tax- R&D RDEC CT600 L55/Tax Comp incorrect value of notional tax (19% v 25%)

ias23043-business-tax-rd-rdec-ct600-l55-tax-comp-incorrect-value-of-notional-tax-19-v-25

IAS23043 Business Tax- R&D RDEC CT600 L55/Tax Comp incorrect value of notional tax (19% v 25%)

25th November 2025

If you have a CTAP period that starts prior to the start of the RDEC Merged Scheme. Therefore the calculation of notional tax should be using 25%.

1.The R&D RDEC entry screens will be correct

2. The Tax comp has a RDEC adjustment that is calculated at a incorrect rate of 19% (should be 25%)

3. The CT00L Box L55 may be showing a value using a rate of 19% incorrectly (should be 25%)

4. The RDEC credit calc should be a mix of 19% and 25% but its all calculated incorrectly at 19%

5. There are incorrect carry forward values

This is a DEFECT and our IRIS Development Team have released a HOTFIX version 25.4.8. Please contact IRIS Support and request this hotfix link be sent to you.

Our apologies for the inconvenience.