For an ordinary ERC-3643 transfer, the token should first reject disallowed token or wallet states and any amount exceeding the sender’s available balance after frozen tokens. It should then verify the recipient through the Identity Registry and require the Compliance contract’s canTransfer(from, to, amount) pre-check to pass. Only after those gates succeed should it move tokens and call the compliance state-update hook. Minting, forced transfers, and burns have different rules, so they must not be treated as ordinary transfers.
ERC-3643 preserves ERC-20 compatibility while adding identity, compliance, and token-management controls. It defines interfaces and behaviors; the issuer must supply the offering rules and meet applicable legal obligations. This is implementation guidance, not legal advice. Read the ERC-3643 specification.
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How the control path fits together
Think of a transfer as a sequence of distinct gates rather than a single eligibility check. Identity Registry checks answer whether a wallet is eligible under the required on-chain claims. The Compliance contract checks whether this particular transaction is permitted under offering-level rules. The token itself enforces balances and operational states, then notifies compliance of successful state changes.
- Check token and wallet state: reject a paused token or a frozen sender or recipient, as applicable.
- Check available balance: ensure the sender has enough transferable tokens after subtracting any partially frozen amount.
- Check recipient eligibility: require the recipient to be registered and verified through the Identity Registry.
- Check offering rules: require
canTransfer(from, to, amount)to return true. - Execute and account: move the tokens, then call the appropriate compliance hook so rule state reflects the transfer.
The specification states that “The receiver MUST be whitelisted on the Identity Registry and verified (hold the necessary claims on his onchain Identity).” That receiver requirement is part of ERC-3643’s transfer behavior.
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Which contracts and permissions are involved?
ERC-3643’s architecture separates token administration, identity records, claim policy, and offering compliance. Keep those responsibilities explicit when configuring a deployment; do not assume a single contract performs every check.
| Component | Implementation responsibility |
|---|---|
| Token | Applies token-level transfer behavior, including state and balance controls, and invokes compliance checks and hooks. |
| Identity Registry | Connects wallet addresses to identity contracts and checks whether the required claims are present. |
| Identity Registry Storage | Stores identity registration information for the registry architecture; assess whether storage should be token-specific or shared for the deployment. |
| Trusted Issuers Registry | Identifies issuers trusted to provide claims for the required topics. |
| Claim Topics Registry | Defines which claim topics are required for eligibility. |
| Compliance contract | Evaluates offering-level rules before an operation and updates its state through operation-specific hooks. |
The owner appoints and removes agents, while registry management uses the appropriate agent permissions. Define who may change issuer trust, claim topics, registrations, pause state, freezes, and recovery actions—and limit those permissions to the duties each role needs.
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Set identity eligibility policy
Choose required claims and trusted issuers
Determine which claim topics a holder must satisfy and which issuers are trusted for each topic. Configure the Claim Topics Registry and Trusted Issuers Registry accordingly. Eligibility is therefore a policy decision made by the project, not a universal list imposed by ERC-3643.
Register wallets and verify claims on-chain
Register the wallet-to-identity association in the Identity Registry. During the ordinary transfer path, check the recipient against that registry and the configured claim requirements. This is an on-chain registration and claim check: it does not mean the smart contract performs off-chain KYC or determines whether an investor’s documents are genuine. The issuer’s identity-verification process must feed the appropriate identity and claims into the system.
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Define offering-level compliance rules
Use the Compliance contract for restrictions that apply to the offering or transaction, rather than confusing them with whether a wallet holds the required identity claims. The standard’s examples include limits on the number of holders, country-level holder constraints, and maximum tokens per investor. A project may implement its own compliance logic or use optional modular rules.
- Identity eligibility: required claim topics, trusted issuers, and registration determine whether the recipient is an eligible holder.
- Transaction and offering rules: compliance logic can decide whether the transfer would breach a holder limit, maximum holding, country constraint, or another issuer-defined rule.
Examples of possible modules include country allow or restriction rules, transfer limits, maximum balance, supply limits, and fees. These are examples, not mandatory ERC-3643 modules; the official documentation identifies its module examples as outside the open-source protocol. Choose custom or modular logic based on the offering’s rules and the ability to inspect, govern, and update that logic.
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Separate the compliance pre-check from state updates
canTransfer is a read-only pre-check. It answers whether the proposed operation is permitted under the compliance contract’s current view of state; it is not where the contract should record the transfer as completed. After a successful operation, use the relevant state-update hook, such as transferred, created, or destroyed, to keep compliance accounting current for later decisions.
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For an ordinary transfer, this means a successful pre-check must be followed by the token state change and the transfer accounting hook. Do not update compliance state for a transfer that failed before execution, and do not omit the hook after a successful transfer. Apply the operation-appropriate hook when creating or destroying tokens as well.
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Handle transferFrom, mint, forced transfer, and burn explicitly
Do not assume every token operation follows the same gates as an ordinary transfer. ERC-3643 specifies significant differences for privileged or supply-changing paths.
| Operation | Control behavior to account for | Implementation implication |
|---|---|---|
| Ordinary transfer | Check token and wallet state, transferable balance, recipient verification, and the compliance pre-check; update compliance state after success. | Use the full ordinary-transfer gate sequence. |
transferFrom |
Do not assume that allowance handling makes it equivalent to, or exempt from, the standard’s transfer controls. | Implement the specification’s operation-specific behavior and ensure the delegated path cannot skip required controls. |
| Mint | The described mint path requires a verified receiver but bypasses compliance rules. | Restrict who can mint, check the receiver as required, and update compliance accounting through the creation hook. |
| Forced transfer | The described forced-transfer path requires a verified receiver but bypasses compliance rules. | Treat it as a privileged exception with tightly scoped authority and a documented recovery or intervention process. |
| Burn | The described burn path bypasses eligibility checks. | Enforce appropriate authority and use the destruction hook to keep accounting current. |
These exceptions are not a reason to skip operational safeguards. Minting, recovery, forced transfers, freezes, pausing, and agent permissions should have defined authorization, review, and incident procedures. Do not expose privileged functions to ordinary holders or operators who do not need them.
Plan deployment and operational authority
The official ERC-3643 documentation identifies T-REX as the main protocol and describes an official factory and gateway for deploying a complete contract suite. It also reports that public deployments are disabled and access is restricted to whitelisted association-member wallets. Because access can change, verify the current deployment route and eligibility with the official project documentation before planning a launch. No network-specific factory address or unrestricted deployment route is established here.
Before deployment, assign accountable owners for issuer and claim configuration, compliance-rule changes, agent administration, emergency pauses, wallet and token freezes, recovery requests, and privileged operations. Confirm how those permissions are granted and revoked, and test ordinary and exception paths against the rules the offering actually intends to enforce.
Quick Recap
Implementation checklist
- Define required claim topics and trusted issuers, and decide how wallet identities are registered.
- Specify offering-wide rules independently from holder eligibility checks.
- For ordinary transfers, enforce state and available-balance checks, recipient verification, and a passing compliance pre-check before moving tokens.
- Call the correct compliance state-update hook after a successful transfer, creation, or destruction.
- Implement
transferFrom, mint, forced transfer, and burn according to their operation-specific behavior rather than routing them through assumptions made for ordinary transfers. - Limit and document authority for agents, freezes, pauses, recovery, minting, and forced transfers.
- Verify current deployment access and test the complete contract suite and privileged paths before use.
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