Quick note before we start: I'm a civilian who runs this newsletter. I'm not a veteran, I haven't held a federal contract, and I'm definitely not a lawyer. What follows is what I learned from digging through SBA documentation, the Code of Federal Regulations, and current rule-making activity, written in plain English. For your specific situation, your nearest APEX Accelerator or VBOC is the right call — they're free, and they actually know your industry. Where I cite a rule, I link the original.

The first time I saw a NAICS code, I had no idea what I was looking at.

Six digits. No explanation. Sitting at the top of a federal solicitation like a license plate. The contract said "NAICS 541330" and assumed I'd know what to do with that. I didn't. Most beginners don't. So they skip past it, focus on the dollar amount, and miss that those six digits are the single most important number on the entire page.

Here's why your NAICS code is the bouncer at the door of every set-aside contract — and why getting it wrong (or not understanding it) costs SDVOSBs real opportunities.

NAICS stands for North American Industry Classification System. It's a coding system used by the US, Canada, and Mexico to categorize businesses by what they do. The federal government uses it for almost everything — statistics, tax purposes, contract classification, size determinations.

Every code is a 6-digit number, and the digits go from broad to specific:

So 541330 reads as: Sector 54 (Professional services) → Subsector 5413 (Architectural/Engineering) → Industry 541330 (Engineering Services).

There are roughly 1,000 NAICS codes total. You'll work with maybe 5-15 of them, depending on what your business does.

1. On your SAM.gov registration. You self-select one primary NAICS code (the work you primarily do) plus any number of secondary codes that also fit. Your primary NAICS is what SBA uses to determine your size for SDVOSB certification purposes.

2. On every contract opportunity. When a contracting officer posts a solicitation, they assign a NAICS code to it based on the principal nature of the work. That code is non-negotiable for that specific contract — if you want to bid, you have to be classified as small under that NAICS.

This is where most beginners get tripped up. They assume "I picked NAICS 541330 in SAM, so I'm good for everything." They aren't.

This is the part I really want to make stick, because it's the most common misunderstanding I've seen in beginner content.

Your "small business" status is calculated relative to the NAICS code on the specific contract you're bidding — not your primary NAICS in SAM.

Each NAICS code has its own size standard — a threshold that defines what "small" means in that industry. Size standards come in two types:

The thresholds vary widely. As of late 2024:

So picture a hypothetical SDVOSB doing $20 million a year in mixed engineering and IT consulting work:

Same company, same revenue, three different answers. The NAICS code on the contract is the determining factor every single time.

A few things to know that the SBA documentation says clearly but most subscribers don't:

Revenue is NOT just last year. SBA averages your total receipts over the last 5 completed fiscal years (this changed from 3 years to 5 years in 2022). If your last 5 years were $18M, $22M, $26M, $30M, and $34M, your average for size purposes is $26M — not $34M.

Receipts is NOT net income. SBA defines receipts as all gross revenue from all sources. That includes pass-through revenue from subcontractors. It's a much larger number than what you'd see on the bottom of a tax return as "taxable income." The technical definition lives at 13 CFR 121.104.

Affiliate revenue counts. If your business is owned by, controls, or is connected through ownership to other businesses, those affiliates' revenue gets added to yours. This is one of the most common compliance landmines in federal contracting. The relevant rule is 13 CFR 121.103.

Employee counts use headcount, not full-time equivalents. A part-time employee counts as one person, same as a full-timer.

In August 2025, SBA published a proposed rule to raise size standards across 263 industries. Public comment closed October 21, 2025. The rule isn't finalized yet, but if and when it is, some firms currently labeled "other than small" will become small again under the new thresholds.

A few examples of what's proposed:

If you're an SDVOSB sitting just above the current threshold for your primary NAICS, you may suddenly be eligible for set-asides you couldn't pursue before. Worth watching the SBA's announcements over the next several months. (I'll cover it in the newsletter when it's finalized.)

SBA has a free Size Standards Tool that lets you enter a NAICS code and instantly see the current size standard. Don't memorize the numbers — verify them every time you bid, because they change. Bookmark the tool.

Here's something most subscribers don't know exists.

Sometimes a contracting officer assigns a NAICS code to a solicitation that you think is wrong — typically one with a smaller size standard than you think the work warrants. If you genuinely believe a different NAICS would be more appropriate, you can appeal to SBA's Office of Hearings and Appeals (OHA) within 10 days of the solicitation being posted. The procedure lives at 13 CFR 121.1102-1103.

If OHA agrees with your appeal, the NAICS gets changed and the size standard shifts — which can open the contract to bidders who were previously excluded.

This is a niche tool. Most subscribers will never use it. But knowing it exists is exactly the kind of detail that separates someone who reads federal contracting articles from someone who actually understands how the system works. If you ever see a solicitation where the assigned NAICS feels obviously wrong for the actual work being requested, that's worth a conversation with your APEX counselor about whether an appeal makes sense.

A few things I'd want you to know that don't get emphasized enough in beginner content:

Listing more secondary NAICS codes isn't always better. Some contractors add every plausibly related code to their SAM profile thinking it broadens their reach. In practice, contracting officers searching the SAM database for capable vendors weight a firm's primary NAICS more heavily. Listing 30 codes you don't really do can dilute rather than help. Better to list 5-10 codes you genuinely perform under than 30 you might theoretically perform.

Size compliance is on you, not the contracting officer. When you bid on a small business set-aside, you're self-certifying that you're below the size standard for the contract's NAICS. If a competitor protests your award and SBA finds you weren't actually small, the consequences are serious — contract termination, potential False Claims Act exposure. There have been real cases where firms paid millions to settle false-certification claims.

Recalculate your size before every major proposal. Not just once when you registered. Your 5-year revenue average changes every year. So does the size standard if SBA revises it. The number you assumed last year may not be the number this year.

If you're new to NAICS and want to build the habit:

The thing that finally clicked for me: NAICS isn't just a classification code, it's the gate between you and every set-aside contract in the federal market. The contracting officer is the one who picks which gate each contract goes through. Your job is to know which gates you can walk through, which ones you can't, and where the size standards sit for each.

That clarity is what separates SDVOSBs who chase any contract that looks interesting from SDVOSBs who pursue the ones they can actually win.

If anything in this primer was unclear, or if you spotted something I got wrong, hit reply and tell me. I read everything, and primers like this one get sharper when readers push back on what doesn't quite work. Talk soon.

— Rex Six Figure Set-Aside

None of this is legal advice. For your specific situation, talk to your APEX Accelerator or a federal contracts attorney. Size compliance has real consequences and this is one of the topics where a free 30-minute consultation with someone who knows your industry will save you a lot of grief.