We often get this question from managers, and the answer is simple: in TwoWork, employees register their own sick leave.
As part of our philosophy it is the employees who are empowered to register their own working hours. The EU finds this particularly important. What you need to decide are the rules for how employees should register their working time. The simple rule is that 'they need to register every working day. Also if they are on vacation on a working day.'
TwoWork requires a start and end time even for sick leave. You should decide on a standard and communicate it to your employees - for example: "If you are sick for a full day, register 08:00–15:30 with no break."
Keep in mind that different employees may work different hours. A part-time employee or someone on a different shift will have their own normal working hours. Make sure each employee knows what to enter based on their own schedule.