In Smart Campaigns, the maximum bid is automated to achieve your specified goal. This means that the settings are not editable for Smart Campaigns. The max bid will adjust only when the optimal bid for conversion falls outside of the set constraints. It's important to note that increasing the max bid doesn't mean all bids will rise or reach the maximum. Instead, the max bid for ad groups allows the predictive AI to determine the appropriate value-based bid for specific keywords within the ad group. Even with changes in the max bid, safeguards remain in place to minimize risk in unusual situations. For instance, if you receive an unusually large order, such as 10 times the average, the max bid will prevent your bids from escalating to match that outlier order.

If you run into a situation where you would like to reduce spending for a given ad group you still have the ability to do that through other campaign and ad group settings.

The first option is to adjust your ACOS Limit. By reducing your ACOS limit you are telling the bidder that you have less margin to work with and would like to tighten your spending. This in turn will immediately start to reduce the bids for keywords in the ad group.

A second consideration, in a situation you would like to reduce spending, is to manage your campaign budget. Reducing your campaign budget will ensure that you are not spending over your given threshold.

You can also utilize the bid modifier override within ads manager for Smart Campaigns. This override can be set for 24, 48, 72 hours. The override allows your to set a static bid modifier for the input time period. To reduce cpc's and spending your can reduce the modifier for a period of time. A reduction in the modifier will in turn reduce bids therefore reducing spend.