24 CFR § 982.505 - How to calculate housing assistance payment.
(a) Use of payment standard. A payment standard is used to calculate the monthly housing assistance payment for a family. The “payment standard” is the maximum monthly subsidy payment.
(b) Amount of monthly housing assistance payment. The PHA shall pay a monthly housing assistance payment on behalf of the family that is equal to the lower of:
(1) The payment standard for the family minus the total tenant payment; or
(2) The gross rent minus the total tenant payment.
(c) Payment standard for family—(1) Applying the payment standard. The payment standard for the family is the lower of:
(i) The payment standard amount for the family unit size; or
(ii) The payment standard amount for the size of the dwelling unit rented by the family.
(2) Separate payment standards. If the PHA has established a separate payment standard amount for a designated part of an FMR area in accordance with § 982.503 (including an exception payment standard amount as determined in accordance with § 982.503(d)), and the dwelling unit is located in such designated part, the PHA must use the appropriate payment standard amount for such designated part to calculate the payment standard for the family.
(3) Decrease in the payment standard amount during the HAP contract term. The PHA may choose not to reduce the payment standard amount used to calculate the subsidy for a family for as long as the family continues to reside in the unit for which the family is receiving assistance.
(i) If the PHA chooses to reduce the payment standard amount used to calculate such a family's subsidy in accordance with its Administrative Plan, then the initial reduction to the family's payment standard amount may not be applied any earlier than two years following the effective date of the decrease in the payment standard, and then only if the family has received the notice required under paragraph (c)(3)(iii) of this section.
(ii) The PHA may choose to reduce the payment standard amount for the family to the current payment standard amount in effect on the PHA voucher payment standard schedule, or it may reduce the payment standard amount to an amount that is higher than the normally applicable payment standard amount on the PHA voucher payment standard schedule. After an initial reduction, the PHA may further reduce the payment standard amount for the family during the time the family resides in the unit, provided any subsequent reductions continue to result in a payment standard amount that meets or exceeds the normally applicable payment standard amount on the PHA voucher payment standard schedule.
(iii) The PHA must provide the family with at least 12 months' written notice of any reduction in the payment standard amount that will affect the family if the family remains in place. In the written notice, the PHA must state the new payment standard amount, explain that the family's new payment standard amount will be the greater of the amount listed in the current written notice or the new amount (if any) on the PHA's payment standard schedule at the end of the 12-month period, and make clear where the family will find the PHA's payment standard schedule.
(iv) The PHA must administer decreases in the payment standard amount for the family in accordance with the PHA policy as described in the PHA Administrative Plan.
(4) Increase in the payment standard amount during the HAP contract term. If the payment standard amount is increased during the term of the HAP contract, the PHA must use the increased payment standard amount to calculate the monthly housing assistance payment for the family beginning no later than the earliest of:
(i) The effective date of an increase in the gross rent that would result in an increase in the family share;
(ii) The family's first regular or interim reexamination; or
(iii) One year following the effective date of the increase in the payment standard amount.
(5) PHA policy on payment standard increases. The PHA may adopt a policy to apply a payment standard increase at any time earlier than the date calculated according to paragraph (c)(4).
(6) Changes in family unit size during the HAP contract term. Irrespective of any increase or decrease in the payment standard amount, if the family unit size either increases or decreases during the HAP contract term, the new family unit size may be used to determine the payment standard amount for the family immediately but no later than the family's first regular reexamination following the change in family unit size.