gettxoutproof (0.18.1.5 RPC) gettxoutproof ["txid",...] ( "blockhash" ) Returns a hex-encoded proof that "txid" was included in a block. NOTE: By default this function only works sometimes. This is when there is an unspent output in the utxo for this transaction. To make it always work, you need to maintain a transaction index, using the -txindex command line option or specify the block in which the transaction is included manually (by blockhash). Arguments: 1. txids (json array, required) A json array of txids to filter [ "txid", (string) A transaction hash ... ] 2. blockhash (string, optional) If specified, looks for txid in the block with this hash Result: "data" (string) A string that is a serialized, hex-encoded data for the proof.