Every federal contract gets a Procurement Instrument Identification Number (PIID). One character in that number identifies the instrument type. When you see a C in that position, you are looking at a definitive contract, as opposed to a purchase order (P), a delivery order (D), a task order (J), or a BPA call (A).

That distinction matters because instrument type reflects the acquisition method used to award the contract. Purchase orders are the product of simplified acquisition procedures. Definitive contracts are typically the product of formal competitive source selection under FAR Part 15, or a sole-source justification and approval. The threshold where simplified acquisition ends and formal Part 15 begins depends on what you are buying.

When you are handed a C-type acquisition to work, you are in FAR Part 15 territory. That means a formal Request for Proposals (RFP), a structured evaluation, a Source Selection Authority, and a documented best-value determination. The RFP is the document that sets the rules for the entire competition.

Both the RFP and the Combined Synopsis/Solicitation (CSS) are solicitations. Both are posted on SAM.gov. Both invite offerors to submit proposals. But they operate under different FAR authorities and have fundamentally different structures.

The RFP is the right tool when the government needs to make a judgment call about the quality of proposals, not just the price. It gives you the structure to say: here is what we will evaluate, here is how we will evaluate it, and here is what you need to tell us to get a good score.

FAR 15.204-1 requires RFPs to use the Uniform Contract Format. The UCF divides the document into four parts and thirteen lettered sections. Most sections will eventually become the contract itself. Sections L and M exist only in the solicitation phase. Once award is made, they drop out.

Sections A through J form the contract. Section K covers offeror representations. Sections L and M are where the competition happens. Section L tells offerors how to respond. Section M tells both offerors and evaluators how the government will decide. If you write these two sections well, the rest of the evaluation process runs smoother.

Section L is the offeror's blueprint for building a proposal. It tells them what volumes to submit, how many pages each volume can be, what format to use, and exactly what to address within each evaluation factor. A well-written Section L eliminates ambiguity and makes proposals easier to evaluate because every offeror is responding to the same specific questions.

Section L typically contains:

• L.1 — Proposal Organization Requirements: defines the volume structure, page limits, font, margins, and how to submit (SAM.gov, encrypted email, physical delivery)
• L.2 — Proposal Instructions by Volume: walks through each volume and tells offerors exactly what to address for each evaluation factor
• L.3 — Questions and Clarifications: deadline for questions, the no-contact-with-agency rule, and when the government will issue answers as an amendment
• L.4 — Proposal Preparation Costs: standard clause reminding offerors the government will not reimburse proposal costs
• L.5 — Late Proposals: reference to the late proposal rule (FAR 15.208)

The instructions for each volume should be specific enough that an offeror who follows them exactly will give evaluators everything they need to score the proposal. Vague instructions like "describe your technical approach" produce vague proposals and inconsistent evaluations.

Section M is the government's commitment to offerors about how proposals will be judged. It lists every evaluation factor, states how factors compare to one another, defines the rating scale, and describes the basis for award. Offerors read Section M to understand what will win. Evaluators use it as their authority for every score they assign. The Source Selection Authority uses it to document the best-value tradeoff.

Section M typically contains:

• M.1 — Basis for Award: the best-value or LPTA statement
• M.2 — Evaluation Factors: factors listed in descending order of importance
• M.3 — Relative Importance: explicit statement of how factors compare to one another
• M.4 — Evaluation Criteria: what evaluators will look for within each factor
• M.5 — Rating Definitions: the adjectival or color-coded scale the evaluation team will use

The adjectival rating scale most common in DoD formal source selections uses five ratings for non-price technical factors and a separate scale for past performance:

This is the rule that causes the most problems for new COs and is a recurring finding in protests. Every factor listed in Section M must have corresponding instructions in Section L. Every set of instructions in Section L must correspond to something in Section M. If you ask offerors to address something in their proposal but do not have an evaluation factor for it, you cannot use it to distinguish proposals. If you have an evaluation factor but gave offerors no instructions on how to address it, the resulting proposals will be inconsistent and your evaluation record will be weak.

The alignment check is simple in theory:

• Take every factor and subfactor from Section M. For each one, find the corresponding instruction in Section L. If there is no instruction, add one or remove the factor.
• Take every instruction from Section L. For each one, find the corresponding factor in Section M. If there is no factor, remove the instruction or add a factor.
• Check that page limits in Section L are roughly proportional to factor weight in Section M. Giving a factor 30 pages of instruction but treating it as less important than a factor with 5 pages of instruction sends a contradictory message.

The simplest alignment check: sit down with Section L in one hand and Section M in the other and walk through both simultaneously before releasing the RFP. This is also when your legal counsel review is most valuable.

As of November 2025, FAR Part 15 now describes three source selection methods under the Revolutionary FAR Overhaul (FAR class deviation RFO-2025-15, effective November 3, 2025). The choice belongs in your acquisition plan and shapes every decision about Section L and M.

Best Value Tradeoff (FAR 15.101-1) allows the government to pay more for a technically superior offeror if the SSA documents that the additional value justifies the additional cost. Technical factors, past performance, and other non-price factors are evaluated on an adjectival scale. After evaluation, the SSA makes a tradeoff decision: is the higher-rated, higher-priced offer worth it? A well-documented tradeoff can withstand protest scrutiny. An undocumented one usually cannot.

Lowest Price Technically Acceptable (LPTA, FAR 15.101-2) awards to the lowest-priced offeror whose technical proposal passes a pass/fail threshold. There is no tradeoff. A technically acceptable offeror with a slightly better proposal gets nothing for that superiority. LPTA is appropriate when the requirement is well-defined, performance risk is low, and technical differentiation adds no real value to the government. DoD has statutory restrictions on LPTA use (10 U.S.C. 3241) — it may not be used for information technology, systems development, complex services, or when technical merit is expected to affect program outcomes.

Highest Technically Rated with a Fair and Reasonable Price (FAR 15.103-3) is a new method added by the RFO. It is appropriate when the government determines in advance that it would not be advantageous to consider tradeoffs between price and non-price factors, and that the acquisition warrants paying any fair and reasonable price to get the highest-quality performance. In other words: you want the best, and you will pay for it as long as the price is not unreasonable.

The process works sequentially. Proposals are evaluated on technical factors only. The SSA identifies the highest-rated proposal. That proposal's price is then evaluated for fair and reasonable determination under FAR Subpart 15.4. If the price is fair and reasonable, award is made. If not, the SSA moves to the next-highest-rated proposal and repeats the price check. Price is never a tradeoff factor — it is only a ceiling check.

This method suits acquisitions where the government genuinely needs the best available capability and cannot accept a "good enough" solution — highly specialized research, critical system development, or advisory services where the top-performing offeror provides qualitatively different outcomes. It is also useful where price spread among qualified offerors is expected to be narrow, making a tradeoff analysis a lower-value exercise.

FAR does not mandate how descriptive your evaluation criteria must be. FAR 15.304 requires that the RFP "clearly" identify all evaluation factors and significant subfactors and state their relative importance. The RFO adds that factors must "represent key areas of importance" supporting "meaningful differentiation between competing proposals." Beyond that, how much you spell out within each factor is a judgment call, and COs approach it differently.

Two common styles:

Minimalist: The factor name and subject matter, with little or no description of what evaluators will look for. Section M identifies what the government will evaluate; the detail lives in the SSP (which is internal and not released to offerors).

Descriptive: Each factor or subfactor includes a sentence or two explaining what evaluators will assess and what "good" looks like. Offerors know exactly what to address and evaluators have explicit written standards to apply.

Neither style is required by FAR. Both are legally defensible if consistent with the Section L instructions and the SSP. The practical tradeoffs:

For most services contracts, moderate description is the practical middle ground: name the factor, briefly state what will be assessed, and let the SSP handle the detailed scoring rubric. If your agency has a standard Section M template, use it — consistency across your office's solicitations reduces protest surface and makes evaluator training easier.

Start with Section M. Write your evaluation criteria before you write your proposal instructions. This forces clarity about what actually matters and prevents you from soliciting information you have no plan to evaluate.

Tie Section L instructions directly to the PWS. Reference specific PWS sections in your proposal instructions. If an offeror needs to tell you how they will meet the 98% uptime SLA in PWS Section 4.3, say so explicitly. Generic instructions produce generic proposals.

Avoid using percentages for factor weight. FAR requires you to state relative importance using comparative language ("Technical is significantly more important than price") not percentages. Point systems are permitted but require careful design. Percentages invite mathematical manipulation of proposals and can restrict the SSA's judgment in a tradeoff.

The Source Selection Plan must match Section M. Before releasing the RFP, your Source Selection Plan (SSP) should define the evaluation process. The SSP is internal, but the rating criteria in it must align with what Section M says. Evaluators score against the SSP; offerors propose against Section M. They have to describe the same thing.

Set realistic page limits. Page limits that are too tight produce proposals that can't adequately address the requirement. Too loose and you create review burden without value. A rough guide: 20–30 pages for technical on a mid-complexity services contract, 10–15 for management, and a separate volume for past performance references (usually 3–5 relevant contracts with points of contact).