The charge for interest accrued on bonds is to account 1420.1, Interest, for interest accrued prior to the date of substantial completion, and applicable to the development period, and to account 4716, Interest on Indebtedness, for interest accrued subsequent to the date of substantial completion, and applicable to the operating period. The date of substantial completion is considered as the first day of the operating period. The credit for interest accrued on housing bonds is made to account 2132.1, Accrued Interest Payable—State of New York. A further allocation of interest charges to the cost of related programs should then be made as described in section 1644-2.4 of this Part. However, after the bonds have been issued, the basis for the allocation is the proportion that the amount borrowed for the related program in the bond sale budget bears to the total bond issue. Prior to the issuance of bonds, it will be recalled, the basis of the allocation is the proportion that the amount requisitioned for the related program on the most recent certificate of purposes bears to the total amount borrowed.