NAICS and PSC codes are the plumbing of federal procurement. Get them right and relevant opportunities flow to you; get them wrong and you never see the work you are best positioned to win.

NAICS codes classify your industry, and critically, they carry the size standards that determine whether you count as a small business for a given opportunity. The same firm can be "small" under one NAICS code and "large" under another — which is why agencies' choice of code on a solicitation matters so much.

PSC codes, by contrast, classify what is being bought: a product or a service, described at a finer grain than NAICS. Agencies use PSC codes in their own market research, so aligning your profile to the PSC codes your target agencies actually use makes you easier to find.

The practical move is to look at how your target agencies have coded past awards similar to your work, then mirror those codes in your SAM.gov profile and your capability statements. Choose the codes the government uses to buy, not the ones that merely describe you.