A Letter Contract is a contract and when issued should include all the completed parts of the Uniform Contract Format (UCF) that are known at the time of issuance.  As delineated in FAR 53.215, the following forms are prescribed for use in contracting by negotiation (except for construction, architect-engineer services, or acquisitions made using simplified acquisition procedures):

• Standard Form (SF) 26; Award/Contract – may be used when signature on a single document by both the Government and the Contractor is appropriate.  Block 18 may not be used for negotiated procurements.
• SF 30; Amendment of Solicitation/Modification of Contract – may be used for amending requests for proposals and requests for information
• SF 33; Solicitation, Offer and Award – may be used for solicitation and award
• Optional Form (OF) 307; Contract Award – may be used for award

DFARS 204.7103-1(a) states: Contract line items shall include a single accounting classification citation.

Section G of the UCF includes the funding details for a solicitation or contract.  The DoD uses ACRNs to trace funds from accounting systems to contract actions. An ACRN is assigned to each different accounting classification, often referred to as a line of accounting (LOA), listed in Section G of a contract. The LOA is used to identify the funding source associated with an organization’s budget and to ensure accurate accounting transactions.  The contract may include a single LOA, or it may have many.  The CLINs and SLINs that each ACRN applies to will also be identified in Section G, as well as the amount of funding for each.  A Letter Contract is no different.

Please refer to your agency's policy office to determine if SPS is use to award contracts.  If your agency uses SPS, then Letter Contracts will be awarded through SPS.