## Summary

You can use the following steps to manage an existing merchant account. This
might be your own merchant account, or a client's merchant account.

## Manual steps

Here are the ways you can administer a sub-account:

Administrative user (recommended)
:   If you need to use the [Merchant Center UI](https://merchants.google.com), the
    merchant can add your Google account as an administrative user for their
    Merchant Center account.

Service account (recommended)
:   If you don't need the Merchant Center UI, you can authenticate through
    [a service account](https://developers.google.com/shopping-content/guides/how-tos/service-accounts), then add the service account ID
    as a user on the merchant's account.

Full management (not recommended)

:   We recommend one of the preceding options unless you only need to manage one
    sub-account.

    If the merchant wants you to fully manage their Merchant Center account and
    you have an MCA, you can do the following:

    1. Gather the IDs for your MCA and for the merchant's account.
    2. In the top right menu bar, click the **?** question mark **\> Help center
       and support \> Contact us**.
    3. Request to convert the merchant's account to a sub-account of your MCA,
       and provide the ID of your MCA account and the ID of the merchant's
       account.

       You can contact Google again to undo this process.

## Automatic steps

You can use the Content API for Shopping to request, approve, and remove links
between your MCA and other Merchant accounts. Here are the steps:

1. Use the Content API for Shopping and [authenticate as an OAuth2 client](https://developers.google.com/shopping-content/guides/how-tos/authorizing).
2. [Request a link](https://developers.google.com/shopping-content/guides/flagging/request) to another Merchant account.
3. Ask the merchant to [approve the link](https://developers.google.com/shopping-content/guides/flagging/approve).

You can also use the Content API for Shopping to
[list](https://developers.google.com/shopping-content/guides/flagging/list) and
[remove](https://developers.google.com/shopping-content/guides/flagging/remove) existing links.

Your Shopping solution can present the merchant with a consent screen to give
your OAuth2 application access to their merchant account.

This process still requires use of the [Google API Console](https://console.developers.google.com/) UI.

See [Using OAuth](https://developers.google.com/shopping-content/guides/how-tos/authorizing#OAuth2Authorizing) for more details and sample code.