158.70[Whenever, in respect of the assessment year commencing on the 1st day
of April, 1992, or any earlier assessment year, a registered firm is assessed],
or an unregistered firm is assessed under the provisions of clause (b)
of section 183, the 71[Assessing] Officer shall notify to the firm
by an order in writing the amount of its total income assessed and the
apportionment thereof between the several partners.