IAS23043 Business Tax- R&D RDEC CT600 L55/Tax Comp incorrect value of notional tax (19% v 25%)
Article ID
ias23043-business-tax-rd-rdec-ct600-l55-tax-comp-incorrect-value-of-notional-tax-19-v-25
Article Name
IAS23043 Business Tax- R&D RDEC CT600 L55/Tax Comp incorrect value of notional tax (19% v 25%)
Created Date
25th November 2025
Problem
Resolution
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%.
- The R&D RDEC entry screens will be correct
- The Tax comp has a RDEC adjustment that is calculated at a incorrect rate of 19% (should be 25%)
- The CT00L Box L55 may be showing a value using a rate of 19% incorrectly (should be 25%)
This is a DEFECT and our IRIS Development Team are investigating this for a future fix. Once we have news we shall update this KB. There is no workaround for this.
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