The Registrar may amend an assessment at any time if:
(a) either:
(i) under section 65B, the Registrar has determined that section 65A does not apply to a parent; or
(ii) under section 66A, the Registrar has reduced an annual rate of child support payable by a parent to nil; and
(b) the Registrar becomes satisfied that the parent does not satisfy the condition in subsection 65B(4) or 66A(2) (as the case requires).