Ensuring a supplier's invoice contains a valid VAT registration number is important, particularly if you expect there may be a risk of fraud or if a self billing system is operated.
Invalid or bogus VAT numbers may be used on an invoice by a VAT evader who charges VAT on their invoice to you, but is not a registered supplier. The supplier then fails to account for the VAT to HMRC. If this happens it is quite likely you will NOT be able to recover any VAT paid as HMRC will argue you should have tested the registration number. Use this tool to check the VAT registration number your customer or supplier has given you matches to their details. If you are in any doubt you should check the number on the VIES Database