CT600L boxes L129 and L150 – double counting RDEC step 2 restrictions carried forward

Due to an error in HMRC’s online service, our software must calculate box L150 incorrectly in order for the return to be accepted for electronic filing.

HMRC describes the issue here (bottom of the page): Changes and issues affecting the Corporation Tax online service - GOV.UK (www.gov.uk)

A new pre-step 1 section has been added to the CT600L for customers to report the amount of step 2 restriction brought forward from previous accounting periods.

Any balance not used and carried forward to the next accounting period is captured in new boxes L8 and L129.

The figure in box L129 is correctly included in box L140 — balance carried forward to next accounting period, but has been captured twice in box L150 — total carried forward to next accounting period.

This means that all software packages will be reporting an incorrect figure in box L150, but this is used by HMRC for statistical purposes only.

The figure in box L129 should be the one included in box L5 in your next Corporation Tax Self Assessment.

We expect this to be the case until 1 April 2023.