(1) Subject to section 139Q, if the income that a bankrupt is likely to derive during a contribution assessment period as assessed by the trustee under an original assessment exceeds the actual income threshold amount applicable in relation to the bankrupt when that assessment is made, the bankrupt is liable to pay to the trustee a contribution in respect of that period.
(2) Subject to section 139Q, if the income that a bankrupt is likely to derive during a contribution assessment period as assessed by the trustee under an original assessment does not exceed the actual income threshold amount applicable in relation to the bankrupt when that assessment is made, the bankrupt is not liable to, but may if he or she so wishes, pay to the trustee a contribution in respect of that period.