A National Stock Number, or NSN, is the 13-digit code that uniquely identifies every supply item tracked in the U.S. federal and NATO logistics systems. More than 8 million active items carry one. The number lets military branches, civilian federal agencies, and allied nations refer to the same product by the same identifier, whether they are ordering it, storing it, or issuing it downrange.
What the 13 Digits Mean
Every NSN follows the same layout: a 4-digit Federal Supply Classification code, then a 9-digit National Item Identification Number (NIIN). Written out, an NSN looks like 5120-00-123-4567.
The first four digits are the Federal Supply Class. They place the item in a commodity category. FSC 5120, for instance, covers non-powered hand tools. The first two digits of the FSC identify the broader Federal Supply Group, of which there are 79. Groups subdivide into classes; a group covering hand tools generally will have separate classes for edged and non-edged tools.
The remaining nine digits are the NIIN, the item’s unique fingerprint. Its first two digits are the National Codification Bureau code, showing which country cataloged the item. The United States uses NCB codes 00 and 01. The last seven digits are a non-significant sequential number, meaning the digits themselves encode nothing about the item; they only distinguish it from every other item in its class.
Who Uses NSNs
The Department of Defense is the largest user, but the system reaches well beyond the military. The General Services Administration uses NSNs so civilian federal agencies can requisition products through its Global Supply program, which brings any federal buyer into the same catalog.
Internationally, the NATO Codification System ensures that allied nations use one identifier for one item. When a NATO member’s logistics unit orders a replacement part, the NSN tells every participating country’s supply chain exactly which product is needed, regardless of catalog language or manufacturer. That matters most during joint operations, where a misidentified component can delay a repair or put the wrong part on a vehicle.
For contractors, the NSN is the reference number that connects a commercial product to the federal supply chain. A manufacturer’s own part number is unique within that company. The NSN is what makes the item findable across every federal database and requisition system.
How an NSN Gets Assigned
NSN assignment is a government-to-government function. Only a National Codification Bureau can assign one, and only a government agency can request one. Private manufacturers and contractors cannot apply directly.
The process usually starts when a military unit or federal agency identifies a need for an item it will procure, stock, or issue repeatedly. The requesting agency gathers technical data, including the manufacturer’s Commercial and Government Entity (CAGE) code and part number, and submits a cataloging request through its service logistics command. That command forwards the request to the Defense Logistics Agency’s Logistics Information Services division, which reviews the data, classifies the item, and assigns the NSN.
Once assigned, the NSN and its associated data live in the Federal Logistics Information System (FLIS). Corrections and updates to catalog records now go through a digital interface that replaced the older DD Form 1685 paper process.
Within the United States, DLA manages the Federal Catalog System under authority originally established in the Federal Property and Administrative Services Act. Each participating country maintains its own National Codification Bureau responsible for cataloging items within its borders.
How Commercial Vendors Fit In
You do not need an NSN to start doing business with the government. The NSN comes after a government agency decides your product belongs in the federal supply system, not before.
The route for vendors starts with registering in SAM.gov, the federal government’s primary contractor registration and solicitation portal. From there, companies can respond to solicitations posted on SAM.gov or on the DLA Internet Bid Board System at dibbs.bsm.dla.mil. Each military service and major purchasing agency also runs a small business office to help vendors navigate the process. Once an agency decides an item will be repeatedly bought or stocked, that agency initiates the cataloging request that produces the NSN.
Looking Up an NSN
The primary government lookup tool is WebFLIS, the Web Federal Logistics Information System. It supports searches by NSN, NIIN, item name keyword, part number, or manufacturer CAGE code, along with advanced filters for item characteristics, medical supply data, and weapons system associations. WebFLIS requires controlled access through a Common Access Card, External Certificate Authority, or Federal Bridge authentication, so it is not open to the public.
For public users, DLA offers PUB LOG, a free downloadable product updated monthly. PUB LOG provides NSN data, Federal Supply Classification information, and CAGE codes without the access restrictions of WebFLIS, and it is intended for public entities that need cataloging information but lack full FLIS credentials.