Multi-Input Transaction

Overview

A multi-input transaction contains two or more sources that jointly fund or authorize one transaction. In a UTXO model, each input references a specific unspent output from an earlier transaction and supplies the unlocking data required to spend it. The values of all valid inputs are added together, then allocated across the outputs and the transaction fee.

Wallets create multi-input transactions when no single UTXO is large enough for the intended payment. They also use them for consolidation, batching, coin selection, and fee management. Each referenced output can have a different locking condition, so the transaction may require several Digital Signatures or scripts. The transaction is atomic: nodes either accept all inputs together or reject the transaction.

Input selection affects privacy and cost. Combining outputs associated with different addresses can reveal that one entity probably controls them, while a larger input count increases serialized size and usually raises fees. A wallet should also avoid selecting an input already used by another pending transaction, because that creates a double-spend conflict. Replacing or rebuilding the transaction can change its transaction ID.

Payment and treasury systems should distinguish multi-input structure from a Multi-Output Transaction. Multiple inputs describe funding sources; multiple outputs describe destinations. Reconciliation should inspect every input, output, fee, and change output rather than assuming the sender field shown by an explorer represents a single originating account.

For Multi-Input Transaction, the practical test is whether the documented evidence supports this conclusion: a multi-input transaction combines several spendable sources atomically, increasing funding flexibility but also size, fee cost, and privacy exposure. Teams should retain the protocol version and underlying records needed to reproduce the Multi-Input Transaction decision.