VATREC6072 - Transmission of invoices by fax: Customers
The customer may use the faxed invoice as evidence for input tax deduction. But you should consider verifying orders, payment, etc, on selected invoices received by fax as a safeguard against double claiming against both original and fax copies. You should also bear in mind that plain paper fax machines or PCs with a fax facility produce very high quality documents, which may not be easily recognisable as faxes.