If you close or sell your business, you need to tell HM Revenue & Customs (HMRC) within 30 days.
If you close or sell your business you may need to cancel your VAT registration. However, if you sell your business as a going concern or transfer it to another legal entity, then in some circumstances the new owner can apply for your registration number to be reallocated to them.
This guide outlines the steps you need to take.
HM Revenue & Customs