Double-spending is the risk that a unit of digital value is used in more than one payment. It can arise when transactions are accepted before a shared system can verify that the value has not already been spent. Unlike physical cash, digital records can be copied or submitted through multiple devices.
This risk matters most when payment systems operate offline or synchronize later. A device may approve and store a payment locally without checking the latest balance, leaving duplicate transactions to be detected during reconciliation. Defenses include secure storage, transaction limits, tamper-resistant devices, and controls that reject or resolve conflicting records when systems reconnect. These measures help maintain payment integrity, but delayed verification can still create fraud, disputes, and recovery work.