48 C.F.R. § 204.1603
(3) Position 9.
(A) DoD will use three of the letters reserved for departmental or agency use in FAR 4.1603(a)(3) in this position as follows:
(1) Use M to identify purchase orders and task or delivery orders issued by the enterprise FedMall system.
(2) Use S to identify broad agency announcements and commercial solutions openings.
(3) Use T to identify automated requests for quotations by authorized legacy contract writing systems. See PGI 204.1603(a)(3)(A)(3) for the list of authorized systems.
(2) (ii) Positions 2 through 6. In accordance with FAR 4.1603(b)(2)(ii), DoD-issued supplementary PIIDs shall, for positions 2 through 6 of modifications to contracts and agreements, comply with the following:
(1) Positions 2 and 3. These two digits may be either alpha or numeric characters, except—
(i) Use K, L, M, N, P, and Q only in position 2, and only if the modification is issued by the Air Force and is a provisioned item order;
(ii) Use S only in position 2, and only to identify modifications issued to provide initial or amended shipping instructions when—
(a) The contract has either FOB origin or destination delivery terms; and
(b) The price changes;
(iii) Use T, U, V, W, X, or Y only in position 2, and only to identify modifications issued to provide initial or amended shipping instructions when—
(a) The contract has FOB origin delivery terms; and
(b) The price does not change; and
(iv) Use Z only in position 2, and only to identify a modification which definitizes a letter contract or a previously issued undefinitized modification.
(2) Positions 4 through 6. These positions are always numeric. Use a separate series of serial numbers for each type of modification listed in paragraph (b)(2)(ii) of this section.
[81 FR 9785, Feb. 26, 2016, as amended at 88 FR 55938, Aug. 17, 2023]