Wadiah
In one sentenceA safekeeping contract in which the owner hands his money to another party to keep for him and return on demand.
Simply put
In a pure Wadiah the custodian does not guarantee the money unless it acts with misconduct or negligence. But if the owner permits the custodian to use it, the custodian guarantees its full return, which is why current accounts in Islamic banks are treated as guaranteed and earn no return.
In your business's books: the current account balance with the bank is cash with no return. If the business holds money for others (deposits or refundable guarantees), it records it as a liability, not revenue.
Example
A contractor received 30,000 SAR from a client as a guarantee deposit, refundable when the project ends. The contractor records it as a liability (customer deposits) and returns it as is, without recording it as revenue.
Don't confuse it with
Qard HasanIn a loan the money passes to the borrower to use and repay the same amount; in Wadiah the basic principle is that the money is kept for its owner.