37 U.S.C. § 1014: Payment date for pay and allowances

(a) Amounts of basic pay, basic allowance for housing, basic allowance for subsistence, and other payments of military compensation (other than travel and transportation allowances and separation allowances) shall be paid on the first day of the month beginning after the month during which the right to such compensation accrues. (b) Subsection (a) does not preclude one payment in midmonth for any element of compensation and does not affect any authority to make advance payments of pay and allowances. (c) With respect to a member of the uniformed services who has elected to participate in the Thrift Savings Plan under section 211 of this title, subsection (a) does not preclude the payment of an amount equal to one-half of the monthly deposit to the Thrift Savings Fund otherwise to be made by the member in participating in the Plan, which amount may be deposited in the Thrift Savings Fund at midmonth.