Na šalteru plaćam pristojbu gotovinom.

Because šalter (a service counter/window/desk) is conceptualized as a “surface/point of service,” so Croatian commonly uses na + locative: na šalteru = “at the counter.”
U šalteru would literally suggest being inside the counter (not idiomatic).

Šalteru is locative singular. You can tell because:

• The preposition na can take locative (location: “where?”) or accusative (movement: “where to?”).
• Here it’s location (plaćam happens there), so it’s na + locative → na šalteru.

Then you’d use na + accusative:

• Idem na šalter. = “I’m going to the counter.” Locative answers “where?”; accusative answers “where to?”

Pristojbu is accusative singular (direct object).
The verb plaćati / platiti typically takes a direct object in the accusative: plaćam (što?) pristojbu = “I pay a fee.”

Pristojba is a fee/charge, often an official or administrative one (e.g., a stamp duty, administrative fee, processing fee). You’ll see it in formal contexts: offices, documents, applications.
In everyday speech you might also hear naknada (a general “fee/charge”) depending on context.

Gotovinom is instrumental singular of gotovina (“cash”).
Instrumental is commonly used to express the means/method (“by/with what?”):

• Plaćam gotovinom. = “I’m paying in cash.”

Yes, often both are possible:

• Plaćam gotovinom. (instrumental = “by means of cash”)
• Plaćam u gotovini. (prepositional phrase = “in cash”) Both are natural; gotovinom is a bit more compact.

Croatian usually doesn’t require subject pronouns because the verb ending shows the person:

• plaćam = “I pay / I’m paying” You can add ja for emphasis or contrast:
• Ja plaćam pristojbu gotovinom. = “I’m the one paying…”

It’s present tense, and Croatian present can correspond to either:

• “I pay” (habitual/general), or
• “I’m paying” (right now), depending on context. In a real-life situation at the counter, it naturally reads as “I’m paying.”

They’re typically linked as imperfective vs perfective:

• plaćati → plaćam (imperfective): the process / ongoing / general paying
• platiti → platim (perfective): completing the payment (“pay up / pay and finish”)

In many practical situations you’ll hear both:

• Plaćam pristojbu gotovinom. (describing what you’re doing)
• Plat(it) ću pristojbu gotovinom. (I will pay / I’ll pay it)

Croatian word order is fairly flexible, but changes emphasis:

• Na šalteru plaćam pristojbu gotovinom. (neutral; setting first)
• Pristojbu plaćam gotovinom na šalteru. (emphasizes the fee)
• Gotovinom plaćam pristojbu na šalteru. (emphasizes paying in cash)

The most “natural” order often puts context/place early and new information later, but it depends on what you’re stressing.

Šalter usually means a service counter/window in places like:

• post office, bank, police station, city office, ticket office
  It’s less like a kitchen counter (pult) and more like an official/customer-service counter.

This sentence is already neutral. In real interactions you might add polite framing, for example:

• Molim vas, želim platiti pristojbu gotovinom. = “I’d like to pay the fee in cash, please.” Or if you’re answering a question about payment method:
• Gotovinom, molim. = “Cash, please.”