When perfection by possession occurs, the parties must have a written security agreement.

Perfection

The series of legal steps a secured party takes to protect its right in collateral from other creditors that want to have their debts returned through the same collateral.

Possession

The act of having or holding property in one's control; this can range from ownership of land to possession of items or goods.

Security Agreement

An agreement in which a debtor gives a secured interest to a secured party.