Zaposleni je primio obračunski listić.

Here, zaposleni means employee and functions like a noun, even though it originally comes from an adjective.

A useful contrast is:

• On je zaposlen. = He is employed.
  Here zaposlen is an adjective.
• Zaposleni je primio obračunski listić. = The employee received a payslip.
  Here zaposleni is being used as a noun: the employee.

So in this sentence, zaposleni is best understood as a standard noun-like form meaning employee.

Je is the 3rd person singular present form of biti = to be, and here it is used as an auxiliary verb to form the past tense.

So:

• je primio = received / has received

In modern Serbian, this is the normal way to express the past:

• auxiliary je
• plus the past participle primio

English separates received and has received, but Serbian often uses the same form in places where English might choose either one depending on context.

Primio is the masculine singular past participle of primiti = to receive.

It agrees with the subject:

• zaposleni je primio = a male employee received
• zaposlena je primila = a female employee received
• zaposleni su primili = male or mixed group received
• zaposlene su primile = female group received

So primio tells you that the subject is understood as masculine singular.

It is the direct object, so it is in the accusative case. But for many masculine inanimate nouns, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: obračunski listić
• accusative: obračunski listić

No visible change appears here, even though the case has changed grammatically.

The same applies to the adjective:

• obračunski agrees with listić
• masculine singular inanimate accusative looks the same as nominative

So the phrase is grammatically in the accusative, even though its form does not change.

This is a formal administrative expression. It usually means something like:

• payslip
• pay statement
• salary slip
• sometimes earnings statement

The adjective obračunski comes from obračun, which has to do with calculation, accounting, or pay calculation.

The noun listić literally means small slip or slip of paper.

So the phrase is something like calculation/pay slip, but in natural English payslip is usually the best translation.

Because je is a clitic, and Serbian clitics normally go in the second position of the clause.

So the neutral order is:

• Zaposleni je primio obračunski listić.

The first element is Zaposleni, and then the clitic je comes right after it.

This is a very important Serbian word-order rule. Clitics such as je, sam, si, se, ga, mu, and others usually do not stand freely wherever you want.

Yes, Serbian word order is more flexible than English, but not completely free.

The sentence given is a neutral, natural order:

• Zaposleni je primio obračunski listić.

Other orders are possible for emphasis, for example:

• Obračunski listić je primio zaposleni.
  This can emphasize who received it.
• Zaposleni je obračunski listić primio.
  This sounds more marked or stylistic.

Even when the order changes, the clitic je still tends to stay in second position.

Because Serbian has no articles like English the and a/an.

So Serbian often leaves definiteness to be understood from:

• context
• word order
• the situation
• vocabulary choice

In this sentence, zaposleni is naturally understood as the employee or simply an employee, depending on context. Since you said the meaning is already shown to the learner, the Serbian sentence itself does not need an article.

The verb form would change to match the subject.

Examples:

• Zaposlena je primila obračunski listić.
  The female employee received a payslip.

• Zaposleni su primili obračunski listić.
  The employees received a payslip / payslips.

• Zaposlene su primile obračunski listić.
  The female employees received a payslip / payslips.

So when learning Serbian, it is important to notice that the past form agrees with the subject in gender and number.