An IOU, short for “I owe you,” is a record that acknowledges a debt between two parties. Traditionally it is a simple document that states one person or business owes a certain amount to another. In crypto, the same idea appears as a digital IOU, a token or on-chain balance that represents a promise to deliver an underlying asset later.
How IOUs work in cryptocurrency
In blockchain systems, an IOU usually represents a claim on an issuer rather than a native coin. Instead of holding the base asset directly, the holder owns a transferable obligation that says, in effect, “the issuer owes the bearer this amount of a specified asset.” This is common when a platform needs to represent off-chain assets on-chain, such as fiat currency, commodities, or even a cryptocurrency that is custodied elsewhere.
A practical example is an exchange credit: if a trading platform shows you a balance of BTC, that balance can function like an IOU if the platform is the custodian and you do not control the private keys. Similarly, some networks support issued currencies, where a gateway issues on-chain IOUs that can be sent between users, while redemption requires trusting the issuer to honor withdrawals. The XRP Ledger historically referred to these as IOUs, issued currencies that track obligations between accounts.
Benefits, risks, and what to watch
IOUs can make markets more efficient by enabling fast transfers and trading of representations of real-world or custodied assets. However, they introduce counterparty risk: if the issuer becomes insolvent, freezes withdrawals, or refuses redemption, the IOU may lose value even if the underlying asset exists somewhere.
This concept matters in the crypto ecosystem because it highlights a core tradeoff between convenience and self-custody, helping users understand when they truly own an asset and when they merely hold a promise from someone else.