How a customer ID works
Every Google Ads account is given a customer ID when it is created. It is ten digits long, written in three dash-separated blocks, and it sits at the top right of the interface next to the account name. It never changes for the life of the account, which is exactly what makes it useful: names get edited, email addresses change hands, but the ID stays put.
It is the identifier every linking process asks for. Inviting an account into a manager account, connecting Google Analytics, joining a Merchant Center feed, granting a colleague access, filing a support request, authenticating an API call — all of them are keyed on the customer ID rather than on the account name. A manager account has its own customer ID too, which is a common source of confusion when someone is asked for “the ID” and sends the wrong one.
Why the customer ID matters
It removes ambiguity in the one situation where ambiguity is expensive. Businesses often run several accounts — one per country, one per brand, one left over from a previous agency — and they frequently share a similar name. When you ask an agency to be removed, or a developer to pull reporting, the customer ID is what guarantees the change lands on the account you meant.
It is also how you audit your own estate. Listing every ID you own, and who has access to each, is the fastest way to discover an account nobody remembered that is still charging a card every month.
Common mistakes with customer IDs
The most frequent is mixing it up with the other identifiers floating around a marketing stack. A GA4 property ID, a Merchant Center ID, a conversion ID and a Tag Manager container ID all look like anonymous strings of digits, and pasting one where another belongs produces a link that silently never works.
The second is treating the number as a secret. It is not a password and it grants nothing on its own — access still has to be invited and accepted inside the account. The genuine risk runs the other way: cold callers claiming to be from Google often quote a customer ID to sound legitimate, because it is visible to anyone who has ever had access. Quoting your ID is not proof of anything.
How to act on it
Keep a simple written record of every advertising account the business owns, each with its customer ID, the email address that owns it, the payment method attached and who currently has access. Check it when staff leave and when agencies change.
When you are asked for an ID, ask which one — the advertising account or the manager. When someone contacts you unprompted about your account, end the call and sign in yourself to check. And before consolidating anything, settle the account structure you actually want, because IDs are permanent and campaign history does not move between them.