Learn Finnish: Sairausloman jälkeen työntekijän on tuotava lääkärin todistus. - After the sick leave, the employee must bring a doctor's certificate.

This sentence uses the [genitive subject] + on + [passive present participle] structure to express obligation. Here, työntekijän (the employee's) is the genitive subject, followed by on, and then tuotava (is to be brought), which is the participle form of tuoda (to bring). Together, it literally means "of the employee is to be brought", or more naturally, "the employee must bring".

How is the participle tuotava formed from the verb tuoda?

To form this participle for a type 2 verb like tuoda, you take the stem by removing the infinitive ending -da (leaving tuo-) and add the ending -tava. This creates tuotava.

Why is the object todistus in its basic nominative form instead of taking a genitive object ending like -n?

Normally, a complete action takes a total object ending in -n. However, there is a special rule for sentences expressing necessity or obligation (including this structure, as well as sentences using täytyy or pitää): their total objects always take the basic nominative form. That is why we see todistus. The word lääkärin is just a genitive modifier meaning "doctor's".

Why are both sairausloman and in the genitive case?