You will find this function in the Timeline view:
Balance can be corrected for a certain person on a certain day by clicking on the day on the timeline and inputing the positive or negative amount of hours.
For example, when an employee has a balance of +40 hours (overtime) and you pay them for these extra hours, you need to enter -40:00 to get their balance back to zero.
Make sure you use the proper format: xx:xx (for example: 06:37 - 6 hours and 47 minutes). The corrected balance will also be seen in the exported reports.