A special type of security interest provided for under the Uniform Commercial Code (UCC) that enables a seller who sells goods on credit to obtain a superpriority security interest in the goods to secure the buyer's obligation to pay the deferred purchase price. This is possible even if the goods constitute after-acquired property of the buyer subject to a previously perfected security interest in favor of a third party, such as the buyer's asset-based lender (UCC § 9-324).

PMSI also enable a third-party lender (such as a bank) who lends money to a borrower for the express purpose of enabling the borrower to purchase specified goods to obtain a superpriority security interest in the goods if the buyer uses the credit to purchase them.

In each case, the UCC sets filing and other rules the seller or lender must comply with to establish the PMSI. For more information on PMSI, see Practice Note, Purchase Money Security Interests (PMSI).