VATREG39600 | Registration in respect of relevant supplies: post-registration action at assurance visits
From HM Revenue & Customs · VAT Registration
Businesses should be examined to confirm that they continue to fulfil the Schedule 3A registration requirements, or whether they have ever fulfilled these requirements.
Where a person has been admitted to the register under the VAT Act 1994, Schedule 3A but it is later discovered that their activities:
have changed or
are incompatible with the requirements of this schedule
the procedures detailed in section 68 should be followed.