Section 20 of the Principal Act is amended -
(a) in subsection (5)(a) by substituting "unless they determine that the refund of that overpaid amount or part thereof would result in the unjust enrichment of the claimant" for "unless that refund would result in the unjust enrichment of the claimant", and
(b) by substituting the following for paragraphs (b), (c) and (d) of subsection (5):
"(b) A person who claims a refund of an overpaid amount under this subsection shall make that claim in writing setting out full details of the circumstances of the case and identifying the overpaid amount in respect of each taxable period to which the claim relates. The claimant shall furnish such relevant documentation to support the claim as the Revenue Commissioners may request.
(i) For the purposes of determining whether a refund of an overpaid amount or part thereof would result in the unjust enrichment of a claimant, the Revenue Commissioners shall have regard to -
(I) the extent to which