## Existing Merchant Center Account - Existing Account Connection

It is imperative to allow your merchants to use their existing Merchant Center account if they choose to. This account has a lot of historic data and can potentially make the onboarding easier (for example, account has been policy approved already).

### UX Guidance

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There could be two scenarios in which a merchant already has an existing Merchant Center Account.

**Scenario #1. They have one existing account:**
![1_MC](https://developers.google.com/static/merchant/storebuilder/images/blueprint/1_MC.png)

Account connected:
![1_MC_1](https://developers.google.com/static/merchant/storebuilder/images/blueprint/1_MC_1.png)

Account created and connected:
![1_MC_2](https://developers.google.com/static/merchant/storebuilder/images/blueprint/1_MC_2.png)

**Scenario #2. They have multiple existing accounts:**
![1_MC](https://developers.google.com/static/merchant/storebuilder/images/blueprint/1_MC.png)

Select from drop-down and click "connect":
![2_MC_2](https://developers.google.com/static/merchant/storebuilder/images/blueprint/2_MC_2.png)

Account connected:
![1_MC_1](https://developers.google.com/static/merchant/storebuilder/images/blueprint/1_MC_1.png)

Account created and connected:
![1_MC_2](https://developers.google.com/static/merchant/storebuilder/images/blueprint/1_MC_2.png)

### Tech Guidance

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If your merchant already has an existing Merchant Center Account they want to use, follow these steps to successfully use their account:

1. Identifying the Merchant Center account: Use the content API endpoint [`account.authinfo`](https://developers.google.com/shopping-content/reference/rest/v2.1/accounts/authinfo) with the OAuth credentials of the Google Account of the merchant to display the MC account associated with the Merchant's Google Account.

2. Storing Data: Make sure to store the Merchant sub-account details

3. Existing Not part of your MCA: The MC account will not be a sub-account of your MCA. It is possible for them to be part of a different MCA and still connect to your integration.

4. Account linking: You should use [`account.link`](https://developers.google.com/shopping-content/reference/rest/v2.1/accounts/link) to link your MCA to the merchant's existing accounts. You will manage the merchant MC account only via the content API using OAuth. Note: More information on account linking (account flagging) can be found [here](https://developers.google.com/merchant/storebuilder/online/sections/1_3_account_linking) within this guide.

5. Overwriting existing data: We recommend notifying your merchants by connecting their existing Merchant Center account, their product data and existing settings will be overwritten.