Here’s how to set an Account Spending Limit…
This process is found in Payment Activity within the Billing section. There, you’ll click the “Payment Settings” button. Then scroll down to the An Account Spending Limit is the lifetime limit on the amount your ad account can spend across all of the campaigns that you're running. This is a limit set by the advertiser within the Payment Settings. You can edit, remove, or reset your Account Spending Limit at any time. More section. Click the three dots on the right and select “Set Limit.” There you can enter your Account Spending Limit.
This limit applies to all ads that are running under the ad account. It begins counting towards your limit from the moment you set it. No previous spend will apply.
Once you Reach measures the number of Accounts Center Accounts (formerly users) that saw your ads at least once. You can have one account reached with multiple impressions. More your Account Spending Limit, all ads within your ad account will pause. You can track your progress toward this Spending Limit within Payment Activity. If you need to, you can increase the limit, reset it, or remove it.
The primary reason you may want to use this is for a client. This can give you more control over the total amount that you’re spending.