Vuokra maksetaan kuukausittain viimeistään kuun viidentenä päivänä.

Maksetaan is the Finnish passive (impersonal) present form of the verb maksaa (to pay). Finnish often uses the passive to talk about rules, obligations, or general procedures without naming a specific person:

• It roughly corresponds to English is paid / must be paid / is to be paid depending on context.
• The implied payer is “people involved” (here: typically the tenant), but the sentence stays impersonal on purpose (common in contracts and instructions).

Yes, vuokra (rent) functions like the grammatical subject of the passive clause: “rent is paid…”. In Finnish, the passive does not require an explicit subject, but you can still have a noun like vuokra in the basic nominative form stating what the rule is about.

-taan / -tään is a typical passive ending in the present tense. The exact shape depends on vowel harmony and stem type. For maksaa, the passive present is maksetaan.
You can think of it as “someone/people pay(s)” or “it gets paid,” without saying who.

Kuukausittain is an adverb meaning “monthly / on a monthly basis.” It’s built from kuukausi (month) + the adverb-forming element -ttain / -ittäin, which often expresses “by/at each unit”:

• päivittäin = daily
• viikoittain = weekly
• kuukausittain = monthly

Yes, both are common:

• kuukausittain sounds a bit more “official/administrative” and compact (good for contracts).
• joka kuukausi is very common in everyday speech and feels more literal (“every month”).

In many contexts they’re interchangeable, but kuukausittain fits the style of this sentence well.

Viimeistään means “at the latest / no later than.” It sets a deadline: payment can be earlier, but not later than the stated date. In Finnish it typically appears right before the time expression it limits, as here.

Finnish expresses “on (a certain date/day)” using cases rather than a preposition like on. Here, viidentenä päivänä uses the essive case (-na/-nä), which is commonly used in date expressions to mean “on (that day/date).”

So viidentenä päivänä is literally something like “as the fifth day,” but idiomatically it functions as on the fifth day.

Because it must agree with päivänä (day-ESSIVE). The ordinal viides (fifth) takes the same case as the noun it modifies:

• nominative: viides päivä
• essive (used for dates): viidentenä päivänä

The stem changes slightly (viides → viiden-) before the essive ending -nä.

Yes: kuu can mean both moon and month depending on context.
Kuun is the genitive form (“of the month”), so kuun viidentenä päivänä = “on the month’s fifth day” → idiomatically “on the 5th (day) of the month.”

You may also see kuukauden viidentenä päivänä (using kuukausi), which is clearer and more explicit.

Often, yes. In many contexts you can drop päivänä and still be understood:

• viimeistään kuun viidentenä = “no later than the 5th (of the month)”

But in formal writing, keeping päivänä can sound more complete and explicit.

Finnish word order is fairly flexible, but changes emphasis. This sentence uses a very neutral, formal order:

• Vuokra (topic) + maksetaan (verb) + kuukausittain (frequency) + viimeistään… (deadline)

You could move time expressions earlier for emphasis, e.g.:

• Vuokra maksetaan viimeistään kuun viidentenä päivänä kuukausittain (less natural/clear)
• Kuukausittain vuokra maksetaan viimeistään kuun viidentenä päivänä (emphasizes “monthly”)

The given order is the most standard for a rule.

Finnish main stress is almost always on the first syllable:

• VIE-den-te-nä (stress on VIE-)

Also, Finnish sounds are quite regular: each letter is pronounced, and vowels are “pure” (not heavily reduced like in English).