Learn Finnish: Annamme uuden ohjeistuksen, jottei osasto tee enää virheitä. - We provide the new guidelines, so that the department doesn't make mistakes anymore.

It is a fusion of the conjunction jotta (so that) and the 3rd person singular negative verb ei (doesn't). Because the negative verb is absorbed into jottei, the main verb of that clause (tehdä) appears in its present connegative form, tee.

Would jottei change if the subject of the second clause wasn't osasto?

Yes, because the negative verb part must still match the subject. If the sentence was 'so that we don't make mistakes', you would combine jotta with emme to get jottemme tee. Here, osasto (the department) is a 3rd person singular subject, so it uses jotta + ei = jottei.

Why do the two objects in this sentence, uuden ohjeistuksen and virheitä, use different cases?

Uuden ohjeistuksen is the object of the affirmative verb annamme (we give), so it takes the total object case, which looks like the genitive here. However, virheitä is the object of a negative clause (jottei... tee). In Finnish, objects of negative sentences must always be in the partitive case.

Why does the sentence use ohjeistuksen instead of the plural ohjeet?