(a) In the case of gas producers’ cooperative associations organized and operated as cooperative corporations pursuant to Chapter 1 (commencing with Section 3001) of Part 4 of Division 1 of the Public Utilities Code, whose income is principally derived from the sale in the regular course of business of tangible personal property other than water, agricultural products or food sold at wholesale, all patronage refunds paid or accrued to patrons if the patronage refunds are made and allocated as follows:

1. (1) Made pursuant to a preexisting obligation which is created by the association’s bylaws or other written instrument.
2. (2) Made from earnings which are attributable to business done by the association with the patrons to whom the patronage refunds are made, and allocated ratably according to patronage.
3. (3) Allocated, and the patrons to whom the patronage refunds are to be made are notified of the allocation, on or before the due date for the filing of the association’s franchise tax return, including any extension of time, pursuant to this part, for the year in which the patronage occurred.