An invalid transactionA transaction is a record of an event that occurred in the past. Transactions typically occur during the course of... Read More is a blockchain transactionA blockchain transaction is a digital recording of an event or action stored in a public, decentralized ledger. A blockchain... Read More declared invalid by the network. Invalid transactions can be due to errors in the code, incorrect user input, or double spendingDouble spending is a fraud technique that involves using the same digital currency to make two or more separate purchases.... Read More.