If an amount has been paid by way of social security payment, or by way of fares allowance under the Social Security (Fares Allowance) Rules 1998 , the amount is a debt due to the Commonwealth if, and only if:
(a) a provision of this Act, the 1947 Act, the Social Security (Fares Allowance) Rules 1998 or the Data-matching Program (Assistance and Tax) Act 1990 expressly provided that it was or expressly provides that it is, as the case may be; or; or
(b) the amount:
(i) should not have been paid; and
(ii) was paid before 1 January 1991; and
(iii) was not an amount to which subsection 245B(2) of the 1947 Act applied.