A sick note (Krankschreibung, Arbeitsunfähigkeitsbescheinigung or AU-Bescheinigung) is a document you get from a doctor. It confirms that you are sick, and that you should take sick leave.

The Krankschreibung is a small yellow piece of paper. It looks like this.

Many German employers ask for a sick note if you are sick for more than 3 days1. They can ask for a sick note on the first day1.