Does the federal government buy on-line?

Yes, the Federal Government buys on-line. The federal government continues to move the purchasing process to the internet. For example,

The U.S. General Services Administration (GSA) hosts a website called GSA Advantage and a purchasing system called e-Buy. GSA Advantage is the online shopping and ordering system that provides access to thousands of contractors and millions of supplies (products) and services.  A GSA contract is required to participate in GSA Advantage and in e-Buy.

The Defense Logistics Agency (DLA) hosts the Internet Bid Board System (DIBBS) to purchase supply items.

The Department of Defense (DOD) hosts an on-line system called FedMall.

Unison Marketplace (click here) is a commercial system used by a number of federal agencies to purchase commercial goods and services using a reverse bid process.