# Migrate Customers
source: https://developer.mastercard.com/open-finance-us/documentation/financial-institution/oauth-connections/migration-customers/index.md

You can choose how you want to manage new customers and migrating existing customers accounts moving from a legacy connection to a new OAuth connection.

**Manage Account options**:

* Use the [Migration Service](https://developer.mastercard.com/open-finance-us/documentation/financial-institution/oauth-connections/migration-customers/index.md#migration-service) to move customer accounts.
* Wait for the legacy connection to expire as indicated in the communicated migration plan from the CSM team. Any accounts remaining on the legacy connection are automatically migrated the OAuth connection.

## Migration Service {#migration-service}

Use [Migrate Institution Login Accounts](https://developer.mastercard.com/open-finance-us/documentation/financial-institution/oauth-connections/migration-customers/index.md#migrate-institution-login-accounts) to automatically change information needed to move customer accounts from a financial institution's (FI) legacy connection to an OAuth connection.

The migration service does the following:

1. Changes the FI ID from the legacy connection and updates the FI ID for the OAuth connection.
2. The aggregation status code of the account is set to code 948. Use this status coded to prompt the customer to authenticate their accounts using the new OAuth method.
3. The financial institution transaction identifier is formatted to ensure deduplicating transactions.

Tip: Use the `institutionSettings: autoreplace` feature so that only OAuth institutions are listed in the search list of a Data Connect session as you migrate to a new OAuth connection. See [Financial Institution Search List](https://developer.mastercard.com/open-finance-us/documentation/connect/connect-institutions-settings/index.md).

## Final Migration Steps {#final-migration-steps}

Program your applications to do the following:

1. Indicate to the customer that their FI has updated their connection, and they must sign into their account to reauthenticate on the new connection.
2. Use the [Generate Data Connect Fix](https://developer.mastercard.com/open-finance-us/documentation/connect/generate-2-connect-url-apis/index.md#data-connect-fix) API to set the `institutionLoginId` account.
3. Present Data Connect Fix application pages to the customer.

#### Migrate Institution Login Accounts {#migrate-institution-login-accounts}


API Reference: `PUT /aggregation/v2/customers/{customerId}/institutionLogins/{institutionLoginId}/migration`

**See also**:

* [Register Applications](https://developer.mastercard.com/open-finance-us/documentation/financial-institution/oauth-connections/register-your-applications/index.md)
* [OAuth Connections](https://developer.mastercard.com/open-finance-us/documentation/financial-institution/oauth-connections/index.md)