Siinä tapauksessa, että tosite puuttuu, käsittelijä pyytää selvitystä.

Siinä tapauksessa, että is a formal way to say if or in the event that.

• siinä = in that
• tapauksessa = case/situation in the inessive case, so in the case
• että = that

So the structure is literally something like in that case that ...

In everyday Finnish, this could often be shortened to jos:

• Jos tosite puuttuu, käsittelijä pyytää selvitystä.

The longer version sounds more formal, administrative, and written, which fits this kind of sentence.

The ending -ssa is the inessive case, which often means in.

The basic noun is tapaus = case, situation

• nominative: tapaus
• inessive: tapauksessa = in the case / in the situation

So siinä tapauksessa literally means in that case.

This is a very common expression in formal Finnish:

• tässä tapauksessa = in this case
• siinä tapauksessa = in that case

Here että introduces the content of the condition.

So:

• siinä tapauksessa = in that case
• että tosite puuttuu = that the receipt/document is missing

Together they form a set phrase:

• siinä tapauksessa, että ... = in the event that ...

This is similar to English formal expressions like:

• in the case that ...
• in the event that ...

In simpler Finnish, että disappears if you use jos instead:

• Jos tosite puuttuu ...

Tosite is a formal administrative/accounting word. It often means something like:

• receipt
• voucher
• supporting document
• proof document

The exact English word depends on context. In office, accounting, or reimbursement language, tosite is usually some document that proves a payment, expense, or transaction.

So it is not just any random proof; it often refers to a specific required document.

Because puuttua works differently from the English verb to lack / to be missing.

In Finnish, the thing that is missing is usually the subject:

• Tosite puuttuu. = The receipt is missing.

So:

• tosite is in the nominative singular
• puuttuu agrees with it in the singular

Compare:

• Kuitti puuttuu. = The receipt is missing.
• Liite puuttuu. = The attachment is missing.

If there were several missing documents:

• Tositeet puuttuvat.

Puuttuu is the 3rd person singular present tense of puuttua.

Here it means:

• is missing
• is absent
• is lacking

This verb is very common in formal and everyday Finnish:

• Nimi puuttuu listalta. = The name is missing from the list.
• Yksi sivu puuttuu. = One page is missing.

A useful point for English speakers: Finnish often expresses this idea with the missing thing as the grammatical subject, not with a structure like we do not have.

Because käsittelijä is the subject of the main clause.

• käsittelijä = handler, processor, case officer, staff member dealing with the matter
• pyytää = requests
• selvitystä = an explanation / clarification

So the main clause is:

• käsittelijä pyytää selvitystä

That means the handler/case officer requests clarification.

The word käsittelijä is often used in bureaucratic or administrative contexts for the person who processes an application, case, claim, or document.

Because pyytää very often takes its object in the partitive, especially when referring to something requested in a general or indefinite sense.

Base form:

• selvitys = explanation, clarification, account

Partitive singular:

• selvitystä

So:

• pyytää selvitystä = request clarification / request an explanation

The partitive here does not necessarily mean some in a vague English sense, but it often signals that the requested thing is not being treated as a fully specific, completed whole.

This is a common pattern:

• pyytää apua = ask for help
• pyytää neuvoa = ask for advice
• pyytää lisätietoja = ask for more information

Yes, in some contexts selvityksen could be possible, but it would sound a bit different.

• pyytää selvitystä = request clarification/explanation in a general sense
• pyytää selvityksen = request a specific explanation/report as a whole

In administrative Finnish, pyytää selvitystä is very natural and common. It sounds like asking the person to provide clarification.

So the partitive is the most expected choice here.

Finnish often uses the present tense for:

• rules
• instructions
• standard procedures
• general truths

So:

• käsittelijä pyytää selvitystä does not necessarily mean one specific person is requesting it right now
• it means this is what the case officer does in such a situation

English does the same thing quite often:

• If the document is missing, the officer requests clarification.

So this is a normal procedural present.

Because the sentence begins with a subordinate clause, and Finnish normally separates it from the main clause with a comma.

Structure:

• subordinate clause: Siinä tapauksessa, että tosite puuttuu,
• main clause: käsittelijä pyytää selvitystä.

This is similar to English punctuation in:

• If the receipt is missing, the case officer requests clarification.

The comma helps mark the boundary between the condition and the main statement.

Yes, Finnish word order is fairly flexible, but this version is the most natural for formal written language.

Current order:

• Siinä tapauksessa, että tosite puuttuu, käsittelijä pyytää selvitystä.

A simpler version:

• Jos tosite puuttuu, käsittelijä pyytää selvitystä.

You could also rearrange parts for emphasis, but in official language the given order is clear and standard:

1. condition first
2. result second

That makes the sentence easy to process.

It is natural, but definitely formal and bureaucratic.

Things that make it sound formal:

• siinä tapauksessa, että instead of jos
• tosite
• käsittelijä
• selvitystä

A more everyday version might be:

• Jos kuitti puuttuu, käsittelijä pyytää lisäselvitystä. or even more simply, depending on context:
• Jos kuitti puuttuu, sinulta pyydetään selvitys.

So the original sentence is perfectly good Finnish, especially in official instructions, forms, or administrative decisions.

A helpful way is to divide it into three chunks:

1. Siinä tapauksessa

   • in that case

2. että tosite puuttuu

   • that the supporting document is missing

3. käsittelijä pyytää selvitystä

   • the case handler requests clarification

This kind of chunking makes long formal Finnish much easier to read. It also helps you see that the sentence has:

• a condition
• then a main action

That pattern is very common in administrative Finnish.