Final answer:
The manager is using performance control when comparing monthly sales revenue to the amount forecasted.
Step-by-step explanation:
The type of internal control that the manager is using when comparing monthly sales revenue to the amount forecasted is performance control.
Performance control is a type of internal control that focuses on comparing actual performance with planned or expected performance. It helps managers evaluate the effectiveness and efficiency of their operations and make necessary adjustments to achieve their goals.
In this case, the manager is comparing the actual sales revenue with the forecasted revenue. By doing this, the manager can identify any significant deviations and take appropriate actions to address them. For example, if the actual revenue is lower than forecasted, the manager may investigate the reasons behind it and implement strategies to improve sales.