(1) As soon as practicable after the start of each contribution assessment period in relation to a bankrupt, the trustee is to make an assessment of the income that is likely to be derived, or was derived, by the bankrupt during that period, of the actual income threshold amount that is applicable in relation to the bankrupt when the assessment is made and of the contribution (if any) that the bankrupt is liable to pay in respect of that period under section 139S.
(2) If at any time, whether during or after a contribution assessment period, any one or more of the following paragraphs applies or apply:
(a) the trustee is satisfied that the income that is likely to be derived, or was derived, by the bankrupt during that period is or was greater or less than the amount of that income as assessed by the last preceding assessment in respect of that period;
(b) the base income threshold amount increased or decreased after the making of the last preceding assessment in respect of that period and before the end of that period;
(c) the trustee is satisfied that the number of the bankrupt's dependants increased or decreased after the making of the last preceding assessment and before the end of that period;
the trustee is to make a fresh assessment of the income that is likely to be derived, or was derived, by the bankrupt during that period, of the actual income threshold amount that is applicable in relation to the bankrupt when the assessment is made and of the contribution (if any) that the bankrupt is liable to pay in respect of that period.
(3) The powers of the trustee under subsection (2) may be exercised on the trustee's own initiative or at the bankrupt's request, but the trustee is not required to consider whether to exercise those powers at the bankrupt's request unless the bankrupt satisfies the trustee that there are reasonable grounds for the trustee to do so.
(4) As soon as practicable after the making of an assessment the trustee must give to the bankrupt written notice setting out particulars of the assessment and informing the bankrupt about the possibility of a variation under section 139T.