ERC-3643 Explained: Permissioned Security Tokens
What ERC-3643 (T-REX) is, how the identity registry, claim topics, and transfer restrictions work, and why institutions use it for RWA tokenization.
What is ERC-3643?
ERC-3643 (also known as T-REX) is the institutional standard for compliant security tokens on EVM chains. Unlike open ERC-20 tokens, ERC-3643 enforces who may hold and transfer the token at the smart-contract level.
Only verified, whitelisted addresses can hold or transact. Compliance rules execute automatically on every transfer — without a manual back-office review for each settlement.
PazaLabs issues RWA tokens on ERC-3643 so mortgage pools, hard assets, and receivables inherit permissioned transfer controls from day one.
Identity registry
Each token holder's verified identity is stored in an on-chain identity registry. The registry is controlled by a trusted identity issuer (the compliance provider) and is queried on every transfer.
If the recipient is not registered or no longer verified, the transfer fails atomically. That is the core difference between a permissioned security token and a free-floating fungible token.
Claim topics
Investors must hold valid claims — for example KYC verified, accredited investor status, or jurisdictional approval — to hold the token.
Claims expire and must be renewed, which keeps compliance status current across the asset lifecycle instead of treating onboarding as a one-time event.
Transfer restrictions
Smart-contract transfer rules are configurable: restrict by jurisdiction, investor category, lock-up period, or holding limits.
Rules execute atomically — no transfer completes unless every check passes. Issuers can also support forced transfers and recovery where regulators or authorised parties require it for sanctions, error recovery, or legal orders.
How a compliant transfer settles
1. Sender initiates transfer with the recipient address.
2. Contract queries the identity registry: is the recipient verified?
3. Required claims are checked for validity and expiry.
4. Jurisdiction, category, and lock-up rules are evaluated.
5. If all checks pass, the transfer settles on-chain and the compliance audit trail is updated.
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