Vakuutusyhtiö voi hyvittää laskun jälkikäteen.

Because Finnish very often forms compound nouns as a single word.

• vakuutus = insurance
• yhtiö = company

So vakuutusyhtiö literally means insurance company.

This is extremely common in Finnish. Where English often uses two words, Finnish often uses one compound word.

Voi is the 3rd person singular present tense of voida, which means can, to be able to, or sometimes may.

Here the subject is vakuutusyhtiö = the insurance company, which is singular, so the verb is:

• minä voin = I can
• sinä voit = you can
• hän/se voi = he/she/it can

So Vakuutusyhtiö voi... means The insurance company can...

Because after the modal verb voida, the main verb usually appears in the first infinitive, which is the dictionary form.

So the pattern is:

• voi maksaa = can pay
• voi korvata = can compensate
• voi hyvittää = can credit / reimburse

That is why you get voi hyvittää, not a separately conjugated second verb.

Hyvittää can mean something like:

• to credit
• to reimburse
• to refund
• to make good financially

In this sentence, it suggests that the insurance company may later compensate for the bill by paying it back, crediting it, or otherwise adjusting it financially.

A useful nuance:

• hyvittää laskun often sounds like crediting or reimbursing the bill
• korvata is a broader verb meaning to compensate, to replace, or to cover

So hyvittää is quite natural when talking about money, charges, or invoices being corrected or paid back.

Because laskun is the object form used here for a total object.

• lasku = bill, invoice
• laskun = the bill / bill as a completed object

In a positive sentence like this, when the action is seen as affecting the whole bill, Finnish typically uses the total object. In the singular, that often looks identical to the genitive form.

So:

• hyvittää laskun = reimburse/credit the whole bill

Compare that with the partitive:

• hyvittää laskua = reimburse some of the bill, reimburse it partially, or speak about it in a more incomplete/open-ended way

So laskun tells you the bill is treated as a complete object.

Jälkikäteen is an adverb meaning:

• afterwards
• later
• after the fact
• retroactively

In this sentence it tells you when the crediting/reimbursement can happen: not immediately, but later.

So the idea is that the insurance company may credit or reimburse the bill after the fact.

It is best learned as a fixed adverb.

Finnish does not have articles like English a and the.

So:

• vakuutusyhtiö can mean an insurance company or the insurance company
• laskun can mean a bill or the bill, depending on context

The exact meaning is usually understood from the situation rather than from a separate article word.

The sentence uses a very neutral Finnish word order:

• Vakuutusyhtiö = subject
• voi hyvittää = verb phrase
• laskun = object
• jälkikäteen = adverb

So this is a normal, unmarked way to say it.

But Finnish word order is fairly flexible, and changing it can shift emphasis. For example:

• Laskun vakuutusyhtiö voi hyvittää jälkikäteen.
  Emphasizes the bill

• Jälkikäteen vakuutusyhtiö voi hyvittää laskun.
  Emphasizes afterwards

The original version is the most neutral and natural in many contexts.

You would say:

Vakuutusyhtiö ei voi hyvittää laskua jälkikäteen.

Two important things happen:

1. voi becomes negative with ei voi
2. the object changes to the partitive: laskua

This is a very important Finnish rule: in negative sentences, the object is usually in the partitive.

So:

• Vakuutusyhtiö voi hyvittää laskun jälkikäteen.
• Vakuutusyhtiö ei voi hyvittää laskua jälkikäteen.

Yes. Vakuutusyhtiö is the subject, and it is in the nominative singular basic form.

You can see the structure like this:

• Vakuutusyhtiö = subject
• voi = finite verb
• hyvittää = infinitive main verb
• laskun = object
• jälkikäteen = adverb

So grammatically, the sentence is quite straightforward once you identify the object form laskun and the adverb jälkikäteen.