Where—
a taxable person (in this section referred to as "the recipient") provides a document to himself which purports to be an invoice in respect of a taxable supply of goods or services to him by another taxable person; and
that document understates the tax chargeable on the supply,
the Commissioners may, by notice served on the recipient and on the supplier, elect that the amount of tax understated by the document shall be regarded for all purposes as tax due from the recipient and not from the supplier.