Learn Finnish: Suomessa verot maksetaan aina ajoissa. - In Finland, taxes are always paid on time.

Maksaa (to pay) is a type 1 verb. To form the present passive, you take the basic stem maksa-, change the final a to an e, and add the passive ending -taan. This creates maksetaan (are paid / people pay).

Why is verot (taxes) in the basic nominative case here instead of an object case?

In a Finnish passive sentence, the object is put in the nominative case rather than the genitive case. Because we are talking about multiple taxes, it takes the standard plural ending -t to become verot.

Could maksetaan also translate to 'we pay'?

Yes! In spoken Finnish, the passive form is heavily used to mean 'we' do something. However, since the pronoun me (we) is not in this sentence, it functions as a true passive meaning 'taxes are paid' or 'people pay taxes'.

What is the exact grammar behind the word ajoissa (on time)?

It is the plural inessive form of the word aika (time). It literally translates to 'in times', but it is the standard everyday expression for being on time or early enough.