The Federal Acquisition Regulation is the foundation of federal contracting, but it is not the whole structure. Most major agencies publish their own supplements that add clauses, procedures and restrictions on top of the FAR. A contractor who knows the FAR but ignores the supplement is reading only half the rulebook, and the half that is missing often contains the agency’s most demanding requirements.
Why supplements exist
The FAR is written for the whole government, so it has to be general. Agencies have missions, statutes and risks the FAR cannot address one by one. The Defense Department handles classified information and weapons systems. The Department of Veterans Affairs has a statutory preference for veteran-owned firms. NASA buys things no one else buys. The FAR system allows each agency to issue a supplement that implements and, within limits, adds to the FAR. Supplements cannot contradict the FAR, but they can fill gaps and impose additional obligations.
The ones you are most likely to meet
- DFARS, the Defense Federal Acquisition Regulation Supplement, is the largest and most consequential. It carries cybersecurity requirements for covered defense information, specialty metals and domestic sourcing rules, item unique identification, counterfeit parts controls and much more. The DFARS is accompanied by Procedures, Guidance and Information, a companion document that explains how defense contracting officers apply it.
- VAAR, the VA Acquisition Regulation, implements the department’s Vets First contracting preferences.
- HHSAR, DOSAR, AGAR, DEAR, HSAR and the NASA FAR Supplement serve Health and Human Services, State, Agriculture, Energy, Homeland Security and NASA respectively.
- GSAR, the GSA Acquisition Regulation, governs GSA’s own buying, including aspects of the Multiple Award Schedule program.
Not every agency has a formal supplement, and some smaller agencies rely on internal policies and clauses that appear in Section H of a solicitation instead.
How supplement numbering works
Supplements follow the FAR’s structure, which makes them easier to read than they look. The DFARS, for example, places a 2 in front of the FAR part number: DFARS Part 204 corresponds to FAR Part 4, and DFARS clauses appear in Part 252 with numbers in the 7000 series. A clause numbered 252.204-7012 is a DFARS clause on the subject of FAR Part 4, administrative matters, and in this case it is the well-known clause on safeguarding covered defense information. Other supplements use similar prefixes, so a clause numbered 852.something is a VAAR clause and 1852.something is NASA’s.
What supplements tend to add
Supplement clauses commonly address data and reporting systems unique to the agency, security and access requirements, specialized sourcing restrictions, agency-specific small business programs and invoicing portals. They can also change procedures: how task orders are competed, how past performance is collected or how disputes are handled within the agency. Each of these can affect cost, schedule and risk, so they belong in your pricing and your compliance plan.
Reading the FAR and the supplement together
When a solicitation lists clauses, separate the FAR clauses from the supplement clauses and read the supplement ones with extra care, since they are the ones you are least likely to know. Both the FAR and the agency supplements are published at acquisition.gov, where you can read the full text and the history of changes. If you plan to pursue work with a particular agency, spend an afternoon with its supplement before your first proposal. The requirements you learn about there will not surprise you later, and that alone is worth the time.