Learn Finnish: Yrityksen tulee lähettää veroilmoitus tammikuussa. - The company must send the tax return in January.

This sentence uses a formal necessity construction. Just like with the verbs täytyy and pitää, the subject that "must" do something takes the genitive case. Therefore, yritys becomes yrityksen.

Does tulee mean "comes" here?

Normally tulla means "to come", but in the structure [Genitive subject] + tulee + [1st Infinitive], it means "must" or "is required to". It is a formal, written alternative to täytyy or pitää, often used in official instructions, contracts, and business contexts.

Why is the object veroilmoitus in its basic (nominative) form instead of taking an -n ending (veroilmoituksen)?

This is a crucial rule for all necessity sentences. When a necessity sentence has a total object (meaning the action is completely finished), the object takes the endingless accusative, which looks identical to the nominative. If this were a regular sentence like "The company sends...", the object would take the -n ending: Yritys lähettää veroilmoituksen.

What if the company had to send multiple tax returns? How would the object change?