Restrict Who Can Hold It

Limit transfers of your stablecoin to accounts your KYC program has approved, using B20 transfer policies.

Keep your stablecoin within a known set of holders with an allowlist: transfers only settle between accounts your KYC program has approved. You manage the list in the Policy Registry and bind it to the token’s transfer scopes.

Demo

The demo uses a local browser-generated account to submit real transactions on Base Vibenet. If Vibenet or its B20 features are unavailable, it automatically switches to an illustrative offline version.

New to B20? See the B20 Token Standard for the concepts and a full launch walkthrough. These samples target base-std@v1.0.0, viem@2.55.11, and Base Foundry v1.1.1.

Create and Bind a Holder Allowlist

TypeScript

import { parseEventLogs, type Address } from "viem";
import { account, publicClient } from "../../shared/clients.js";
import { POLICY_REGISTRY, b20Abi, policyRegistryAbi, scope } from "../abi.js";
import { sendContract } from "../write.js";

export async function createHolderAllowlist(token: Address, holders: Address[]) {
  const receipt = await sendContract({
    address: POLICY_REGISTRY,
    abi: policyRegistryAbi,
    functionName: "createPolicyWithAccounts",
    args: [account.address, 1, holders],
  });
  const [created] = parseEventLogs({ abi: policyRegistryAbi, logs: receipt.logs, eventName: "PolicyCreated" });
  const policyId = created.args.policyId;
  for (const policyScope of [scope("TRANSFER_SENDER_POLICY"), scope("TRANSFER_RECEIVER_POLICY")]) {
    await sendContract({ address: token, abi: b20Abi, functionName: "updatePolicy", args: [policyScope, policyId] });
  }
  const saved = await publicClient.readContract({ address: token, abi: b20Abi, functionName: "policyId", args: [scope("TRANSFER_RECEIVER_POLICY")] });
  if (saved !== policyId) throw new Error("Policy was not bound");
  return policyId;
}

See the B20 token standard for the complete interface, roles, and policies.

The token returns the new policy ID for both transfer policy scopes.

An allowlist denies every account not in the policy. Seed intended holders before binding it, and retain the PolicyCreated ID.

See Also

Block an Account

Deny a specific address.

Policy Integration (B20 Standard)

Policy hooks in the B20 standard.