Pysäköintivirhemaksu saapui eilen.

It is a compound noun, which is very common in Finnish.

It breaks down like this:

• pysäköinti = parking
• virhe = mistake / violation / offense
• maksu = fee / charge

So pysäköintivirhemaksu is literally something like parking violation fee.

A very important thing about Finnish compounds:

• the last part usually tells you what kind of word it is
• here, the last part is maksu (fee), so the whole word is a kind of fee

English often uses several separate words where Finnish prefers one compound word.

Here it is in the nominative singular, which is the basic dictionary form.

In this sentence, it is the subject:

• Pysäköintivirhemaksu = the parking fine / parking penalty fee
• saapui = arrived
• eilen = yesterday

So the sentence structure is basically:

• Subject + verb + time expression

Because the subject is singular, the noun stays in its basic singular form.

Saapui is the past tense of saapua (to arrive), in the third person singular.

So:

• saapua = to arrive
• saapui = arrived

Why third person singular?

Because the subject pysäköintivirhemaksu is singular:

• Pysäköintivirhemaksu saapui = The parking fine arrived

If the subject were plural, the verb form would change.

Even though it contains several parts, it is still one noun grammatically.

So Finnish treats pysäköintivirhemaksu as:

• one subject
• singular

That is why the verb is singular:

• saapui = singular past

A compound word may look long, but grammatically it behaves like a single word.

Eilen means yesterday.

It functions as a time adverb in this sentence.

Unlike many Finnish words, eilen is simply used as an adverb here; you do not need to analyze it as one of the common noun case forms in this sentence.

So:

• Pysäköintivirhemaksu saapui eilen.
• The parking fine arrived yesterday.

It tells you when the action happened.

Yes, Finnish word order is fairly flexible, but this version is a neutral, straightforward order:

• subject → verb → time expression

So this sentence sounds natural and unmarked.

Other orders are possible, for example:

• Eilen pysäköintivirhemaksu saapui.

This still means the same thing, but it gives more emphasis to eilen (yesterday).

In Finnish, changing word order often changes focus or emphasis, not the basic meaning.

Finnish does not have articles like English a/an and the.

So pysäköintivirhemaksu can mean:

• a parking fine
• the parking fine

Which one sounds best depends on the context.

In a real situation, English would often translate this as The parking fine arrived yesterday or A parking fine arrived yesterday, depending on what has already been mentioned.

Finnish leaves that distinction to context.

Yes, you could.

• saapua = to arrive
• tulla = to come

In many everyday contexts, tuli can also be used when something like a letter, bill, or fine arrives.

The difference is roughly this:

• saapui sounds a bit more like arrived
• tuli can sound a bit more general or conversational, like came

So both can work, but saapui is a very natural choice for something arriving in the mail or otherwise being delivered.

It means that it arrived yesterday, not necessarily that it was issued yesterday.

That distinction is important.

• saapui describes arrival
• it does not by itself tell you when the fine was created, written, or imposed

So the sentence is about when it reached you—for example, in the mail or electronically—rather than when the violation happened.

Because Finnish uses cases, the whole compound changes as one unit.

For example:

• pysäköintivirhemaksu = nominative
• pysäköintivirhemaksun = accusative/genitive-type form depending on context
• pysäköintivirhemaksua = partitive

Examples:

• Sain pysäköintivirhemaksun. = I received the parking fine.
• Maksoin pysäköintivirhemaksun. = I paid the parking fine.
• Odotan pysäköintivirhemaksua. = I am waiting for the parking fine.

A useful rule: in a compound noun, you usually add the case ending to the end of the whole compound, not to each part separately.

A learner-friendly breakdown is:

py-sä-köin-ti-vir-he-mak-su

A few pronunciation tips:

• y, ä, and ö are front vowels that do not exist in the same way in English
• Finnish pronunciation is usually very regular
• stress is normally on the first syllable: PYsäköintivirhemaksu

Also, each written sound is usually pronounced clearly, so long Finnish compounds are often easier to pronounce than they first appear once you break them into parts.