When you hire an agency to manage AdWords campaigns for your business, you will need to give them access to your AdWords account, so that they can create, edit, and track campaigns for you. Furthermore, when the client relationship ends, you should remove that agency's access to your account.
Don't worry, it is very easy to manage. Here are the steps.
Step 1: Share Your AdWords Customer ID with Your Agency
Log in to your AdWords account and find your Customer ID in the upper left corner under the account name. Copy that number and email it to your agency. They will use this number to send you an invitation to grant them access to your account.
The next few steps are up to your agency.
Step 2: Your Agency Invites You to Link Your Account
Once they receive your Customer ID, your agency can send you a request to link to your AdWords account. To do this, they log in to their AdWords Manager Account, click on "Accounts", select the "Management" tab, and click the "+" sign to add your account.
When they click the "+" sign, your agency will have a choice between creating a new account for you or linking to your existing account. Since you already have an account, they should link with it, rather than create a new one.
Once they select "Link existing account", your agency will be presented with a form where they can enter the Customer ID that you shared with them. They will paste the Customer ID into the box labeled "Link existing accounts" and click "Send Invitation". This puts the ball back in your court, as your account is not linked with your agency until you accept the invitation.
Step 3: Accept Your Agency's Invitation
To complete the process, you need to accept your agency's invitation. Of course, you can also reject the invitation if you decide that you do not want them to access your AdWords account.
Log in to your AdWords account, and you will notice that there is an alert labeled "New account access request".
Click on the alert and the Account access page will open. Alternatively, if you don't see the alert, you can open the “Tools, billing, and settings” menu (by clicking on the wrench symbol), and click on the “Account access” menu item.
The request from your agency will appear under the MANAGERS tab in the “Link request” table. Click on the ACCEPT action to complete the linking process.