When is an invoice acceptable without a VAT number?

An invoice is acceptable without a VAT number when the customer is a non-VAT registered entity. This is because businesses are only required to include a VAT number on invoices issued to VAT registered customers. For transactions involving customers who are not registered for VAT, the obligation to include this information does not apply, since non-VAT registered entities are not involved in VAT transactions. Therefore, the absence of a VAT number on such invoices is compliant with VAT regulations.

In contexts like sales to VAT registered customers, samples, or exempt goods, a VAT number would typically be necessary to ensure the transaction is appropriately documented for tax purposes. However, non-VAT registered entities do not have the same requirements, making invoices issued to them valid without a VAT number.