; and (2) procedures to ensure that the number of vouchers provided or made available with respect to any qualified individual complies with subsection (c)(4)(A). 3. Funding (a) In general There is authorized to be appropriated to the Department of Defense, for fiscal years 2018 through 2023, a sum determined by the Secretary of Defense to be equal to the expenses incurred by the Department in providing the benefits described in section 2(c) for such fiscal years. Such sum shall be derived from amounts appropriated in each such fiscal year for Operation and Maintenance, Defense-wide, for the Office of the Secretary of Defense, and shall not to exceed $75 million for the total period beginning with fiscal year 2018 and ending with fiscal year 2023. (b) Transfers to Postal Service (1) Based on estimates The Secretary of Defense shall transfer to the Postal Service, out of any amount so appropriated and in advance of each calendar quarter during which postal benefits under this Act may be used, an amount equal to the amount of postal benefits that the Secretary of Defense estimates will be used during such quarter, reduced or increased (as the case may be) by any amounts by which the Secretary finds that a determination under this section for a prior quarter was greater than or less than the amount finally determined for such quarter. (2) Based on annual determination For each of the fiscal years 2018 through 2022, an annual determination of the amount necessary to correct any previous determination under this section during such fiscal year, and any transfer of amounts between the Postal Service and the Department of Defense based on that annual determination, shall be made not later than 6 months after the end of such fiscal year. (3) Based on final determination A final determination of the amount necessary to correct any previous determination under this section, and any transfer of amounts between the Postal Service and the Department of Defense based on that final determination, shall be made not later than 6