There are two possibilities.

1st Possibility: Count the student as absent.

By leaving a student absent on a reservation, it will not be counted in the remuneration.

2nd Possibility: Work on the rules of remuneration.

In the settings tab, click on payroll and by setting up remuneration rules based on the marginal value of the session.

It will be necessary to register the student with a course card at 0€.