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External accounts are a customer’s registered bank accounts and saved blockchain addresses. They are referenced by ID as the destination for off-ramps (fiat out) in a quote or transaction. A quote’s source is always an OMS wallet, so external accounts are used as destinations, not sources. OMS never holds funds in an external account, it is a reference used on transactions.
External account registration is not yet available in the OMS API. External accounts are provisioned by Polygon during early-access onboarding. To be notified when registration launches, register your interest.

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Share your use case and we’ll reach out when external account registration is available.

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Supported types

ID prefixType
pmCard_Debit card
cpUsBank_US bank account (ACH or wire)
cpIntlBank_International bank account
cpBcAddr_Blockchain address

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Object

{
  "id": "cpUsBank_...",
  "object": "externalAccount",
  "customerId": "cst_...",
  "type": "usBank",
  "status": "verified",
  "network": "ach",
  "bankDetails": {
    "bankName": "Chase",
    "accountNumber": "******4242"
  },
  "createdAt": "2025-01-15T10:34:00Z"
}

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Using an external account in a transaction

Reference the external account ID under destination.wallet.externalAccount in a quote request. The quote source is always an OMS wallet, so an external account is used as the off-ramp destination, for example a bank payout (cryptoToFiat). 
{
  "customerId": "cst_...",
  "source": {
    "walletId": "wlt_...",
    "asset": "usdc",
    "network": "polygon",
    "amount": "500.00"
  },
  "destination": {
    "wallet": { "externalAccount": "cpUsBank_..." },
    "asset": "usd",
    "network": "ach"
  }
}