A working-time account can also fall below zero. In 2011 the Federal Labor Court ruled on when minus hours may be booked. The employer must have paid for the hours in advance, as part of a steady salary, and the employee must be obliged to work them later.
In its reasoning the court uses the word Zeitschuld, a time debt. The ruling also sets a limit. If the employer simply fails to schedule the hours the employee owes, the missing hours do not become the employee’s debt.