FAR vs. Agency Supplements: What Changes, What Doesn’t, And Why It Matters for Small Contractors

If you're navigating the federal procurement maze, you’ve probably heard of the FAR, the Federal Acquisition Regulation. It's the government-wide playbook for how federal agencies buy goods and services. But what many small businesses don’t realize until it’s too late is that the FAR isn’t the only rulebook. Agency-specific supplements, like the DFARS for the Department of Defense or the GSAR, which is part of the broader GSAM for GSA, can and do change the rules.

Here's a breakdown of what the FAR covers, how the agency supplements modify or extend it, and why understanding the difference is essential for staying compliant and competitive in government contracting.

The FAR is universal, but only up to a point. It covers procurement policy for all executive agencies and serves as the foundation for contract types, competition requirements, small-business programs, and standard clauses.

But then come the agency supplements, which include:

• DFARS – Defense Federal Acquisition Regulation Supplement (DoD)

• GSAR – GSA’s regulatory supplement, housed within the GSAM (which also contains non-binding internal guidance)

• HHSAR – Health and Human Services Acquisition Regulation

• NFS – NASA FAR Supplement

• And many others

Each supplement builds on the FAR, adding agency-specific policies, procedures, and interpretations. If the FAR is the federal rulebook, these supplements are like agency-specific expansions or DLCs, they don’t rewrite the main rules, but they can change the gameplay.

What Stays the Same (FAR = The Floor)

Some things are consistent across all federal contracts:

• Contractor responsibility (FAR Part 9) is always required.

• UEI and SAM.gov registration are governed by FAR Part 4 and apply universally.

• Set-aside implementation under FAR Part 19 is required across all executive agencies, but here’s the catch: the actual authority and structure of small-business programs like 8(a), WOSB, SDVOSB, and HUBZone stem from SBA regulations (13 CFR Parts 121, 124, 126, 127, 128). FAR Part 19 simply implements them.

• NAICS code assignment is handled by the contracting officer, based on the primary purpose of the contract. Challenges must be filed with the SBA’s Office of Hearings and Appeals (OHA) within 10 calendar days.

Bottom line: FAR lays out the procedural structure, but the definitions and legal authority often live in SBA regulations, not FAR itself.

What Changes (Supplements = The Ceiling)

Here’s where things shift depending on the agency:

• Solicitation and evaluation rules

• DFARS and PGI 215 add layers to cost realism and pricing evaluations for defense contracts.

• GSA opportunities may involve special terms under GSAR for Commercial Sales Practices or TDR tracking.

• Cybersecurity requirements

• DoD adds DFARS 252.204-7012 (CUI protection) and DFARS 252.204-7021, which implements CMMC. As of 09/15/2025, the final CMMC rule is issued, effective 11/10/2025, with phased implementation over three years.

• Competition exemptions

• While FAR Part 6 governs competition requirements, GSA MAS orders follow FAR 8.4, and are deemed competed if proper procedures are followed. This is a common mistake in compliance reviews.

• GSA “Refreshes”

• These aren’t updates to the GSAM or GSAR themselves. They refer to periodic updates to the GSA MAS solicitation, accepted through Mass Modifications by contractors.

• Micro-purchase threshold (MPT)

• Despite popular belief, agencies don’t adjust this threshold. It’s set government-wide in FAR 2.101, currently at $10,000, and scheduled to increase to $15,000 on 10/01/2025 per the latest FAC.

Why This Matters for Small Businesses

Let’s say you’re targeting GSA or DoD work and have invested in sba 8a certification or women owned small business certification. If you aren’t tailoring your approach to match the specific supplement, you could:

• Miss required clauses or misinterpret evaluation factors

• Submit a proposal that doesn’t comply with agency-specific pricing or cybersecurity rules

• Misunderstand what “full and open competition” looks like under GSA schedules

• Assume set-aside program rules are controlled by FAR when they’re actually set by SBA and implemented differently depending on the agency

This affects not just your Government Contract Proposal Writing, but also your understanding of where your NAICS code for government contractors gives you the best strategic advantage.

Even the best SBIR Grant Assistance won’t help you win if you’re misaligned with the underlying supplement expectations.

How to Stay on Track

To reduce surprises and boost your win rate:

• Always read the clauses, and double-check whether they reference DFARS, GSAR, or other supplements.

• Map your proposal templates to agency-specific expectations.

• Monitor final rules, like the CMMC implementation timeline or changes to SDVOSB certification processes, to avoid being caught flat-footed.

• Challenge NAICS code assignments wisely, you have 10 calendar days from solicitation or amendment to appeal.

• Accept GSA Mass Mods promptly to keep your schedule current, don’t confuse these with changes to the GSAM itself.

Final Thought

Understanding the FAR is just the beginning. Once you’re in the game, you need to know how the rules change depending on who you’re playing with. Agency supplements like DFARS and GSAR aren’t just red tape, they directly shape how contracts are awarded and what it takes to win.

If you're working through the government contracting certification process, managing federal contracting certifications, or trying to crack the code for disabled veteran small business certification, understanding this ecosystem is mission-critical.

Want to get your NAICS strategy right before diving into proposals? Start here with our breakdown on the Top NAICS Codes for Small Business Federal Contracts in FY2025 (So Far).

If you aren't a Squared Compass partner, what are you waiting for? From getting your business set up with specific government set aside programs at both the State and Federal level, to being empowered by a Fractional Capture team to win government contracts, to receiving tailored government contract opportunities Squared Compass delivers immense value which helps propel our partners to success. Schedule a chat withour team today.