(a) Minimum remittances. During each fiscal year subsequent to January 14, 2021, the Postal Service shall remit towards the liabilities identified in § 3030.182 an amount equal to or greater than the amount of revenue collected as a result of all previous rate increases under this subpart during the previous fiscal year, as calculated using the formulas in paragraph (b) of this section, as described in paragraph (c) of this section.

(b) Formulas. (1) The formula for calculating the amount of revenue collected under this subpart during a fiscal year, described in paragraph (c)(1) of this section, is as follows:

(2) The formula for calculating the prorated fraction of retirement obligation rate authority authorized in a particular fiscal year t that was in effect during the most recently completed fiscal year, described in paragraph (c)(2) of this section, is as follows:

(c) Calculations. (1) The amount of revenue collected under this subpart during a fiscal year, as calculated by the formula in paragraph (b)(1) of this section, shall be calculated in three steps. First, the sums of 1 and the amount of retirement obligation rate authority made available under this subpart during each previous fiscal year—prorated to account for mid-year price increases as described in paragraph (b)(2) of this section—shall be multiplied together. This product represents the proportion by which prices were higher during the most recently completed fiscal year as a result of retirement obligation rate authority. Second, to express this net price increase as a proportion of market dominant revenue, the inverse of this product shall be subtracted from 1. Finally, the result shall be multiplied by market dominant revenue for the fiscal year to change the proportion into a dollar amount.

(2)(i) The prorated fraction of retirement obligation rate authority authorized in a particular fiscal year that was in effect during the most recently completed fiscal year, as calculated by the formula in paragraph (b)(2) of this section, shall be a piecewise function of three parts. First, if the retirement obligation rate authority authorized in a particular year was not in effect during the most recently completed fiscal year, the prorated fraction shall be 0. Second, if the retirement obligation rate authority authorized in a particular year was in effect during the entirety of the most recently completed fiscal year, the prorated fraction shall be 1. Finally, if the retirement obligation rate authority authorized in a particular fiscal year was used to raise prices during the most recently completed fiscal year, the prorated fraction shall be the proportion of volume sent during the fiscal year after that rate increase went into effect.

(ii) The proportion in paragraph (c)(2)(i) of this section shall be calculated in four steps. First, the number of days of the fiscal quarter after and including the effective date of the price adjustment including the retirement obligation rate authority shall be divided by the total number of days in that fiscal quarter. This quotient determines the proportion of days in that quarter in which the higher rates were in effect. Second, that quotient shall be multiplied by the market dominant volume from that fiscal quarter to determine the amount of volume during the quarter receiving the higher rates. Third, that product shall be added to the market dominant volume from any subsequent quarters of the fiscal year because the volume in those quarters was also sent under the higher rates. Finally, this sum shall be divided by the total market dominant volume from the fiscal year to determine the proportion of annual volume sent after the rate increase went into effect.