This guide explains FAR Part 51 of the Federal Acquisition Regulation (FAR): Use of Government Sources by Contractors.

Access to a Government ordering system is not permission to use it for every purchase. First, confirm written authorization, contract purpose, and limits before placing the order.

Watch the FAR Part 51 lesson

A contractor’s access to a Government source is conditional. FAR Part 51 addresses eligible use of Government supply sources and interagency fleet vehicles, with authorization, ordering, and accountability requirements.

FAR Part 51: Separate eligibility from authorization

Section 51.101 identifies circumstances in which Government sources may be used, including cost-reimbursement performance, certain other negotiated contracts, qualifying nonprofit work, and a specific security-equipment situation involving classified fixed-price contracts. However, the rules are more nuanced than ‘all contractors qualify’ or ‘fixed-price contractors never qualify.’ Under 51.102, the contracting officer’s authorization identifies the contract and applicable duration, limitations, and conditions. Also, subcontractor authorizations go through the prime with its approval.

Order within the actual permission

Under 51.103, Federal Supply Schedule orders follow the schedule and authorization and include the required authorization information and statement. Government-stock orders use appropriate procedures and assigned codes and cover items required for contract performance. For example, the permission can limit items, facilities, contracts, or amounts. Sections 51.105 and 51.106 address payment and title; purchasing from a Government source does not automatically give a contractor unrestricted ownership or use rights.

Apply separate fleet controls

Subpart 51.2 allows authorized cost-reimbursement contractors to use interagency fleet vehicles for official purposes under specified conditions. Section 51.202 addresses written authorization, insurance, monitoring, and responsibility for unauthorized use costs. However, employee convenience and company-wide access are not substitutes for contract purpose. Next, keep vehicle authorization, permitted users, usage evidence, insurance, and charges connected to the covered performance rather than treating the fleet as a general employee benefit.

A hypothetical example

A buyer has authorization to obtain supplies for a cost-reimbursement contract and wants to combine that order with supplies for commercial work. Next, the team checks the authorization’s contract, item, and duration limits and separates uses outside its scope. Then, it retains the letter and order records and accounts for the supplies properly. However, an existing access code does not expand the contracting officer’s written permission.

Avoid the shortcut

Give the purchasing team a controlled copy of the authorization and a clear expiration check. Before ordering, compare the proposed item and use with the covered contract and any limits. After receipt, retain the source, order, quantity, payment, and accountability evidence. Also, address a request to extend or change access through the appropriate authorized channel. For example, an ordering account may remain technically accessible after a business need changes, but technical access does not establish continuing contractual permission.

Try this exercise

Then, build a preparation worksheet using these fields. This is a GovSuccess practice, not a prescribed Government form.

1. Eligible basis and contract
2. Written contracting-officer authorization
3. Duration and item or value limits
4. Required ordering terms
5. Assigned codes and permitted users
6. Receipt, payment, and accountability
7. Title and use restrictions
8. Fleet controls if applicable

Turn the lesson into an operating decision

Also, use the worksheet with one current contract or proposed action. In addition, keep the documents reviewed, assign an owner to each unresolved issue, and record the basis for the decision. Next, distinguish a regulatory obligation from a GovSuccess preparation practice. Therefore, the worksheet organizes evidence; it does not grant authority, change contract terms, or establish a Government determination.

Official sources

Source check: November 3, 2026 (Central). Codified Acquisition.gov pages retrieved for this package display FAC 2026-01, effective March 13, 2026. Then, check applicable agency deviations and the actual solicitation or contract. Model overhaul text and an implemented agency deviation are not interchangeable.

• FAR Part 51 — codified text
• FAR 51.101
• FAR 51.102
• FAR 51.103
• FAR 51.105
• FAR 51.106
• FAR 51.201
• FAR 51.202
• FAR overhaul and agency deviation guide — contract-specific verification

Build your readiness baseline

Explore GovAssessment for a structured business-readiness baseline based on your answers. However, it does not approve a contract action, certify compliance, or guarantee an award.

General education, not legal or tax advice. Browse all FAR summaries.