OFAC screening for blockchain explained

A plain-language look at how blockchain transactions are checked against US Treasury sanctions lists before money moves.

TL;DR

TL;DR: OFAC screening for blockchain means checking a wallet address, a counterparty, or an entity against the Office of Foreign Assets Control's SDN List before a transaction settles. If the counterparty is blocked, the payment must not go through.

What gets screened on a blockchain

The Office of Foreign Assets Control (OFAC) is the US Treasury office that administers sanctions. The SDN List (Specially Designated Nationals and Blocked Persons List) names people, entities, and, increasingly, crypto wallet addresses that US persons cannot transact with. On a blockchain, the identifiers are wallet addresses and the entities behind them. Screening means comparing those identifiers against the list before value moves.

Why strict liability changes everything

OFAC is a strict liability regime: intent is not required. A party can be penalized even if it did not know a counterparty was blocked. Civil penalties start at $356,000 per violation, and the 50 Percent Rule extends the block to any entity 50 percent or more owned by a blocked person. For a transaction that settles in seconds, the screening has to happen first, not after.

How screening fits an automated flow

agentmail, the screening API at sanctionsai.dev, checks a counterparty before an agent pays. One HTTP call, under 100 ms, returns clean (ALLOW) or flagged (BLOCK) using live data: 947 OFAC-listed crypto wallets and 19,218 SDN names, synced hourly. That turns a compliance requirement into a single step in the payment path.