When running my VAT return why is KEYPrime producing ‘VAT Return 1 of 2. See supplementary return’?

When the total value of VAT corrections for a given period exceeds HMRC’s reporting threshold of £10,000, KEYPrime will generate an additional ‘Supplementary Report’ that must be submitted manually. The figures shown in VAT Return 1 of 2 are submitted as normal under Making Tax Digital (MTD), but they do not include the under or over declaration amounts.

VAT Return Supplementary Report 2 of 2 outlines the under/over amounts that must be submitted manually to HMRC using their dedicated online VAT error reporting form, accessible via your Government Gateway login. In the example above, the amount of £14,651.21 can be reclaimed and allocated against the second invoice generated in KEYPrime.

Following the HMRC link below provides a way to check how to report errors.

https://www.gov.uk/guidance/check-if-you-need-to-report-errors-in-your-vat-return

On 8 September 2025, HMRC introduced a dedicated online form for reporting VAT errors, replacing the now-withdrawn VAT652 form. This new reporting process is accessible through your Government Gateway login.