ACCA ATX ^UK Syllabus A6. Value Added Tax - Timings for Amendments and Chargeability - Notes ^{1 / 4}

HMRC

May amend any obvious errors (e.g. adding up errors) within 9 months of the date of filing

Taxpayer

May amend within 12m of the January filing date

The onus is on the taxpayer to inform HMRC that they are liable to tax - must be done within 6 months of the first tax year  - unless there's no actual tax liability

If no notification is made then penalties will occur