Persons must notify HMRC of a liability to be registered for VAT. The notification must contain the particulars (including the declaration) set out in the relevant form specified in a notice published by HMRC (Value Added Tax Regulations 1995 (SI 1995/2518), reg. 5).
Notice 700/1/2017, para. 14.1 specifies the relevant form and para. 15 states that the paper version of a standard application to register should be sent to the HMRC VAT Registration Service in Wolverhampton.