Sačuvajte račune za povrat troškova.

Sačuvajte is the imperative form of the verb sačuvati.

In this sentence, it means something like keep / save / retain as an instruction.

More specifically, it is:

• 2nd person plural imperative: used when speaking to more than one person
• also the polite singular imperative: used when speaking formally to one person

Related forms:

• sačuvaj = informal singular (keep/save)
• sačuvajte = plural or polite singular

So a sign, instruction, or office notice will very often use sačuvajte.

This is about aspect, which is very important in Croatian.

• čuvati = imperfective
  This focuses more on an ongoing action: to keep, to be keeping, to guard
• sačuvati = perfective
  This focuses on a completed result: to save / keep successfully / preserve

In instructions like this, Croatian often prefers the perfective imperative when the point is to make sure the action is completed.

So:

• Čuvajte račune could sound more like keep the receipts / hold on to them
• Sačuvajte račune stresses make sure you keep/save them

In practice, both can be understandable, but sačuvajte is very natural in this kind of administrative context.

Because račune is the accusative plural, and it is the direct object of the verb sačuvajte.

You ask:

• Sačuvajte što? = Keep/save what?
• račune

The noun changes like this:

• račun = singular nominative
• računi = plural nominative
• račune = plural accusative

So:

• Računi su na stolu. = The receipts are on the table.
  Here računi is the subject.
• Sačuvajte račune. = Keep the receipts.
  Here račune is the object.

The word račun can mean several different things in Croatian, depending on context, for example:

• bill
• receipt
• account
• calculation

In Sačuvajte račune za povrat troškova, it most naturally means receipts or possibly invoices/bills that you need as proof for reimbursement.

So even though račun has several meanings, here the administrative context makes receipts the best interpretation.

This phrase explains the purpose: for reimbursement of expenses.

Breakdown:

• za = for
• povrat = return / refund / reimbursement
• troškova = of expenses

So za povrat troškova means:

• for expense reimbursement
• literally, something like for the reimbursement of expenses

This is a very common administrative/business phrase in Croatian.

It does take the accusative here.

The reason it may not look different is that povrat is a masculine inanimate noun, and in this case its nominative and accusative singular forms are the same:

• nominative: povrat
• accusative: povrat

So after za, the case is still accusative, but the form does not visibly change.

This is very common in Croatian with many masculine inanimate nouns.

Troškova is the genitive plural of troškovi (expenses / costs).

Here it depends on povrat:

• povrat troškova = reimbursement of expenses

This is a common Croatian pattern:

• a noun + another noun in the genitive to show of

Examples:

• povrat novca = return of money
• plaćanje računa = payment of the bill(s)
• popis studenata = list of students

So troškova is in the genitive because it means of expenses.

It can be either:

• more than one person
• one person formally/politely

Croatian uses the same form for both.

So:

• to a friend: Sačuvaj račun.
• to a customer formally: Sačuvajte račun.
• to several people: Sačuvajte račune.

In public notices and instructions, sačuvajte is very common because it sounds appropriate and polite.

Yes. Croatian word order is fairly flexible because case endings show the grammatical roles.

The version you have is the most neutral:

• Sačuvajte račune za povrat troškova.

But other orders are possible, with different emphasis:

• Račune sačuvajte za povrat troškova.
  This emphasizes the receipts
• Za povrat troškova sačuvajte račune.
  This emphasizes the purpose

Even though the order can change, the original version sounds natural and standard for an instruction.

Because Croatian has no articles like English a / an / the.

So račune can mean:

• receipts
• the receipts
• sometimes even your receipts, depending on context

Croatian usually leaves this to context instead of using an article.

That is why a short instruction like Sačuvajte račune is perfectly normal and does not need an extra word for the.

Yes, it is very natural, especially in formal, office, travel, or reimbursement contexts.

You may also hear similar sentences such as:

• Sačuvajte račune.
• Čuvajte račune za refundaciju.
• Molimo, sačuvajte račune za povrat troškova.

The original sentence sounds like a standard administrative instruction:

• clear
• polite
• concise

So it is a very good example of real Croatian usage.