Method and system for fraud prevention via blockchain

A method for determining fraud for a transaction via blockchain, comprising:

• receiving, by a receiving device of a point of sale device, blockchain data for a blockchain, wherein the blockchain data is comprised of a plurality of blocks, each block being comprised of at least a block header and one or more data values, each data value corresponding to a declined payment transaction and including at least an account identifier, timestamp, and point of sale identifier;
• receiving, by the receiving device of the point of sale device, payment credentials associated with a transaction account, wherein the payment credentials include at least a transaction account number;
• executing, by a querying module of the point of sale device, a query on the blockchain data to identify one or more data values where the included account identifier corresponds to the transaction account number;
• determining, by a determination module of the point of sale device, a decline of a payment transaction involving the transaction account based on at least transaction data for the payment transaction and data included in the identified one or more data values;
• and
• electronically transmitting, by a transmitting device of the point of sale device, at least a timestamp, the transaction account number, and a device identifier associated with the point of sale device to a node associated with the blockchain.