Security deposit

In the field of taxation, a deposit is not included as gross income to the receiving party until the depositing party chooses to apply the funds to purchase services. Commissioner v. Indianapolis Power & Light Co., 493 U.S. 203 (1990), provides that a deposit differs from an advance payment because the depositing party has dominion over the funds and retains the right to insist upon repayment in cash. On the other hand, the party making an advance payment retains no right to insist upon the return of the funds as long as the recipient fulfills the contractual agreement.
See more at Wikipedia.org...

Noun
1. the amount of collateral a customer deposits with a broker when borrowing from the broker to buy securities
(synonym) margin
(hypernym) down payment, deposit

Synonymous with the term margin. A cash amount of funds that must be deposited with the broker for each contract as a guarantee of fulfillment of the futures contract. It is not considered as part payment or purchase. Related: margin

Related: Maintenance margin 

See Margin.

DEPOSIT, SECURITY - An amount of money given to a landlord or lessor by a tenant or lessee that can be used by the landlord or lessor to offset damages to the leased property.