My Client Center (MCC) is a source of confusion for my clients. When I agree to manage their AdWords accounts, they’re understandably confused when I tell them they cannot simply add me as a user.
With AdWords, once you connect your email address to a regular AdWords account, you can use your email only for that account. Since I manage multiple accounts and did not want a new email address for each new account, I created an account with My Client Center which allows me to manage all my client accounts from the same log-in.
Since I use the MCC, clients cannot simply give me access to their accounts by adding my as a user. Instead, a client starts by providing the 10 digit account number at the top right of their AdWords account.
I manually add that account number to the MCC, then clients go back into their AdWords accounts and give me approval. I cannot accept a standard invitation to an account at the email address I use with this business.
So if you are new to AdWords and plan to have a third party manage your account, ask if they use MCC. If they are an agency that manages multiple clients, they will ask for your account number. If they do not use an MCC, you may want to ask how many accounts they manage. (Most agencies should have a set-up like mine where MCC is used for all accounts with their clients).
Note that this does not apply to Google Analytics. With Analytics, clients can add me as a regular user in the Admin area. I do ask for high level permissions so I can ensure AdWords and Analytics are connected and create some goals in the accounts.
For me, best practice is not to make any changes to any accounts without first gaining permission from the clients. When I make changes in AdWords, I pause old ads so no historical information is lost. And of course, clients should also have log-in credentials for their own accounts so they can view the work being performed.