IOU

Beginner

Update shuda Aug 19, 2026

What Is an IOU?

IOU stands for "I owe you." It is an informal document that acknowledges a debt one party owes to another, typically involving money, goods, or services.

Unlike formal financial instruments such as bonds or promissory notes, an IOU is usually not a legally binding contract. It serves as a casual record of debt between parties, often used between friends, family members, or businesses that trust each other. The document typically includes the names of the parties involved, the amount owed, and a signature, but it may lack specific repayment terms or legal enforcement clauses.

How IOUs Work

An IOU can take many forms, from a handwritten note to a verbal agreement. In business settings, companies may use IOUs to informally track amounts owed to suppliers, employees, or partners. The simplicity of an IOU makes it flexible, but this same informality introduces uncertainty. Since IOUs are generally not considered negotiable instruments, the party owed money may have limited legal recourse if the debtor fails to repay.

A typical IOU includes the names of both parties, the amount or value of the debt, the date the IOU was created, and a signature. However, IOUs often omit key details such as repayment deadlines, interest rates, or consequences of nonpayment. This lack of specificity distinguishes them from more formal debt agreements, which tend to include clear terms and legal protections for both parties.

IOUs in Cryptocurrency

In the cryptocurrency space, the concept of an IOU has been adapted to describe digital tokens that represent a claim on an underlying asset held by a third party. For example, some platforms issue IOU tokens that represent assets held in custody, allowing users to trade the claim on-chain while the actual asset remains off-chain. These tokens introduce counterparty risk, as holders depend on the issuer's ability and willingness to honor the redemption.

IOU tokens may appear in crypto lending protocols or exchange-based systems where assets are held in custody. Unlike decentralized cryptocurrencies that exist natively on a blockchain, an IOU token represents a promise rather than direct ownership of a digital asset.

IOUs vs. Formal Debt Instruments

IOUs differ from formal debt instruments in several key ways. Bonds are legally binding contracts with defined terms, including coupon payments, maturity dates, and investor protections. Promissory notes also carry legal weight and typically specify repayment schedules and interest rates. In contrast, IOUs are informal acknowledgments of debt that may not be enforceable in court.

This distinction matters in practice. If a borrower defaults on a bond, bondholders generally have legal recourse to recover some or all of their investment. If someone defaults on an IOU, the lender may have limited options beyond pursuing the matter informally. For this reason, IOUs are best suited for situations where trust between parties is already established.