North American Industry Classification System (NAICS) Code

FAR 19.102 puts the designation on the contracting officer: one code and one corresponding size standard per solicitation, keyed to the industry that best describes the principal purpose of the buy, usually the component carrying the greatest share of contract value. SBA's size standard rides on the code, so the designation determines which firms count as small for that competition.

The designation is final unless appealed, and the window is unforgiving. Any adversely affected party has 10 calendar days from issuance of the solicitation, or of an amendment changing the code, to file with SBA's Office of Hearings and Appeals. A decision received before offers are due binds the solicitation; one received after applies only to future procurements of the same requirement (FAR 19.103).

For multiple-award contracts the one-code rule loosens: solicitations issued after October 1, 2028 may divide the acquisition into portions, each with its own code and size standard. Until then a single code covers the vehicle and every order placed under it.