A contract line item number is used to specify the commodities being acquired for traceable accounting classification on a federal government contract. A CLIN is usually located in section B of the contract, and it is vital for reporting and billing purposes within the contractor's accounting system.
The CLIN is used throughout the government's accounting systems to service invoices, and it is the most crucial part of any government contract. Government agencies use the CLIN structure to report on the funding for contracts that utilize money from different accounts. Oversight authorities, such as Congress, use the CLINs to determine whether contract purchases reflect what they authorized.