Check a Bitcoin address

What the check covers on Bitcoin

Bitcoin has the longest public record of any chain, and a check reads it: sanctions designations, darknet market deposits and withdrawals, ransomware payment addresses, scam and phishing proceeds, stolen funds from named exchange incidents, mixing and CoinJoin participation, and the exchanges and services the funds touched on the way.

Because Bitcoin uses unspent outputs rather than accounts, an address is rarely the whole picture. Spending patterns tie addresses into a wallet, so a clean-looking address can belong to a wallet with a history — and an address with one awkward input can belong to a wallet that is otherwise ordinary. The verdict — CLEAN, LOW, MEDIUM, HIGH, CRITICAL — comes with a recommendation and the decision drivers named, so you can tell those two cases apart instead of guessing.

Sanctions matter most here. OFAC lists digital currency addresses as identifiers of designated persons and sets out the definitions in FAQ 559, with the blocking obligation described on its virtual currency FAQ topic page. You can confirm a designation directly in OFAC's list search.

Address format on Bitcoin

Bitcoin has four address shapes in common use, and all of them are valid:

An example of the bech32 form: bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq. Two practical points. Bech32 addresses are case-insensitive but must be sent all-lowercase or all-uppercase, never mixed. And some exchanges still refuse bc1p deposits, so check the deposit screen rather than assuming.

There is no memo or tag on Bitcoin. A venue asking for one is asking about a different network.

What gets frozen on Bitcoin

Nothing, on the chain itself. BTC has no issuer, no blacklist function and no administrator who can immobilise coins — the contrast with USDT, where Tether's terms allow the issuer to freeze tokens and blacklist addresses, is the whole difference between the two assets.

What actually happens to Bitcoin is downstream. An exchange holds a deposit for review, a bank asks where the coins came from, a designation makes an address radioactive for every regulated venue. The coins keep moving; the doors close. That is why a check before you accept a payment is worth more on Bitcoin than on any other chain: there is no issuer to appeal to afterwards, only counterparties who have already decided.

Before you send, after you receive

1. Check the address you were given, before you send and before you accept. The lookup is read-only — no transaction, no fee, no signal to the owner.
2. Look at the reason line. Ransomware and darknet exposure are treated very differently from a distant hop through a large exchange.
3. Do not read a fresh address as a clean one. A new address with no history says nothing about the wallet behind it, which is why clustering exists.
4. If coins you hold come back HIGH or CRITICAL, keep them still and write down the provenance: who paid you, for what, which transaction. Consolidating or splitting them does not remove the history and makes the explanation harder.
5. Respond to a venue's request for information with that record. Screen the next counterparty before the payment, not after.

Free check vs workspace

Occasional payments: run them in the Telegram bot. An OTC desk taking Bitcoin settlement daily wants the same check on the API with the case trail in the workspace — see the OTC desk view.