(1) For the purposes of this section, each of the following amounts is a service provider debt :
(a) so much of an amount paid, or purportedly paid, to an entity as mentioned in subsection 21(1) as represents an overpayment;
(b) an amount that is repayable as mentioned in section 23 (which deals with conditional payments).
(2) A service provider debt is a debt due to the Commonwealth.
(3) A service provider debt may be recovered by the Commonwealth by action in a court of competent jurisdiction.
(4) If an entity is liable to pay a service provider debt, the service provider debt may be deducted from one or more other amounts that are payable to the entity as mentioned in subsection 21(1), and if it is so deducted, the other amounts are taken to have been paid to the entity to the extent of the deduction.