Without a CSS partner, every Shopping bid runs through Google Shopping, which keeps 20 % of it as a margin: of a £1.00 bid, only £0.80 enters the auction. Through a CSS partner your full bid counts, so you pay 20 % less per click at the same position, or bid with 25 % more power at the same budget.

Here is how the two setups work, why both exist and how the switch is completed.

The two models of CSS integration

1. Direct CSS association (recommended for most merchants)

Your existing Merchant Center account stays independent and fully yours. It is linked to the CSS partner at account level: the partner sends a request, and you confirm it.

Account ownership: you keep full ownership and administrative control of your Merchant Center.
Technical disruption: none. Product feeds, campaign structures, Google Ads links and feed integrations such as Shopify, Channable or Feedonomics stay as they are.
Best for: established brands and merchants who run their own Merchant Center, feed tools or marketing team, or work with an agency.

2. Primary MCA sub-account hosting

A multi-client account (MCA) works like an umbrella over several Merchant Center accounts. In this setup, your store sits inside the CSS partner's MCA as a hosted sub-account.

Account ownership: the CSS partner is the parent administrator of the account structure.
Technical setup: the account lives in the partner's central structure, so their team can manage feed setup, diagnostics and compliance settings directly.
Best for: new online shops without a Merchant Center yet, or merchants who hand feed creation and technical optimisation entirely to their CSS provider.

Already a sub-account of another MCA? Moving a sub-account can change the account structure, and access that only came through the parent account can be lost. Before anything is switched, make sure at least one person has direct administrator access to the account itself (in Merchant Center: Settings → Access and services → People and access).

Two ways to connect a Merchant Center to a CSS

Most merchants

Direct CSS association

Your Merchant Centerowned by you

link

CSS partner

Stays connected to your account:

Product feeds
Google Ads links
Feed tools (Shopify, Channable …)

New or fully managed shops

Primary MCA sub-account

CSS partner's multi-client account (MCA)

Shop

Your store

Shop

The partner is the parent administrator and manages feed setup, diagnostics and compliance settings directly.

Comparison overview

Feature	Direct CSS association	Primary MCA sub-account
Merchant Center ownership	You keep full ownership	Hosted under the CSS partner's parent account
Existing feeds	Unchanged	Feeds or APIs may need to be re-linked
Google Ads link	Existing links stay in place	The account may need to be linked to Google Ads
Onboarding	You confirm one request in Merchant Center	The partner sets up or migrates the account
Ideal for	Self-managed or agency-managed shops	New shops and fully managed feed clients

How to complete the CSS link, step by step

Switching your account to a CSS partner takes three steps.

Step 1: Share your Merchant Center ID

Give your CSS partner your Merchant Center ID. You will find it at the top right of Merchant Center, below your account name; it consists of digits only. At csspartner.io you enter it in the setup form we send you after booking, together with your account type and the email address of a Merchant Center administrator.

Step 2: Your CSS partner sends the request

Your CSS partner enters the ID in Google's CSS Center and sends the request to your Merchant Center, either as a direct association or as part of a migration into their MCA.

Step 3: Confirm the request in Merchant Center

A request from your CSS partner now waits in your Merchant Center, and an administrator of the account confirms the Standard CSS Access. Only an administrator can do this, so check that you are signed in to the account whose ID you shared.

Your Shopping campaigns keep running throughout: campaigns, bid strategies, conversion data and history stay in your account. If you are coming from another CSS, Google applies a grace period of up to 14 days before the new CSS takes effect, so cancel your old provider only once the switch is complete.

How the switch is completed

1You
Share your Merchant Center ID
2CSS partner
Sends the request from Google's CSS Center
3Your admin
Confirms the Standard CSS Access in Merchant Center

Campaigns keep running. Bid strategies, conversion data and history stay in your account.

Which model should you choose?

If your shop already runs Shopping campaigns from its own Merchant Center, the direct CSS association is almost always the right path. It brings the full CSS advantage from the moment the switch takes effect, without handing over control of your account or rebuilding feed and API connections.

If you are launching a new shop or want your CSS provider to take over feed management completely, a sub-account in the partner's MCA gives you a fully managed environment.

Which setup fits your shop

Does your shop already run Shopping campaigns from its own Merchant Center?

Yes

Direct CSS association

You keep control of your account, feeds and integrations.

No, or you want your feed fully managed

MCA sub-account

Your CSS provider runs the account structure and feed setup.