VATREG39550 - Registration in respect of relevant supplies: requirements once a business is registered
Once a person is registered under these provisions, all the normal obligations apply.
Most importantly, when a person is registered, he will have to account for VAT on all his taxable supplies (and acquisitions) as well as on his relevant supplies.
All the other obligations such as issuing invoices, submitting VAT returns, and so on are the same as those of any other person registered for VAT in the UK.