Learn Hardcore Malay: Kaunter itu hanya untuk bayaran tunai. - That counter is for cash payments only.

Malay often omits a linking verb in nominal sentences. So Kaunter itu [is] hanya untuk bayaran tunai is correct without an explicit “is.” You don’t need to insert anything.

Can I add adalah/ialah, like “Kaunter itu adalah/ialah untuk bayaran tunai”?

Better not. Style guides discourage adalah/ialah directly before a prepositional phrase like untuk.... More natural options:

Kaunter itu untuk bayaran tunai sahaja.
Kaunter itu ialah kaunter bayaran tunai sahaja. (Here the predicate is a noun phrase, so ialah is fine.) If you do say adalah/ialah untuk..., many will still understand you, but it’s less idiomatic.

What exactly does itu mean here? Is it “that” or “the”? Could it be plural?

itu most often maps to “that,” but in context it can function like “the (aforementioned).”
It does not mark number by itself. Depending on context, kaunter itu can be “that counter” or “those counters.”
To be explicitly plural, you can reduplicate: kaunter-kaunter itu (“those counters”).
Use ini for “this/these”: kaunter ini.

Why does itu come after kaunter? And why is tunai after bayaran?

In Malay, modifiers typically come after the noun:

Noun + demonstrative: kaunter itu (“that counter”)
Noun + adjective/classifier: bayaran tunai (“cash payment”) This is a general pattern: baju biru itu = “that blue shirt.”

Can I move hanya around? What about sahaja/saja?

Yes. Placement affects emphasis/scope:

Hanya kaunter itu untuk bayaran tunai. = Only that counter is for cash (others aren’t).
Kaunter itu hanya untuk bayaran tunai. = That counter is only for cash (no cards there).
Kaunter itu untuk bayaran tunai sahaja. = Same meaning as the previous, with sahaja (synonym of hanya) at the end. Notes:
hanya and sahaja are near-synonyms; saja is the colloquial spelling of sahaja.
On signs, the end position ... sahaja is extremely common.

Why is it bayaran, not bayar or membayar?

bayar = root verb “to pay”
membayar = “to pay” (active verb form)
bayaran = “payment/fee” (a noun with -an) After untuk, both a noun or a verb phrase can follow, but the meaning changes:
untuk bayaran = “for payment” (noun)
untuk membayar = “to pay” (verb) For signage about a counter’s purpose, the noun is crisper: untuk bayaran tunai. A verb version would be possible but clunky here (e.g., untuk membayar secara tunai).

What’s the difference between bayaran and pembayaran?

Both are nouns meaning “payment,” but:

bayaran often means a payment or a fee/charge (“a payment,” “the fee”): bayaran masuk = entrance fee.
pembayaran leans to the act/process/transaction of paying and is more formal: kaunter pembayaran = payment counter; proses pembayaran = the payment process. In your sentence, bayaran tunai or pembayaran tunai both work; the latter sounds more formal/administrative.

Is untuk the only option? What about bagi, kepada, or buat?

untuk = “for” (default, widely used on signs): untuk bayaran tunai
bagi = “for” (more formal/official in some styles): bagi bayaran tunai is possible but less common on signage.
kepada = “to/unto,” used for recipients: bayaran kepada Syarikat ABC = payment to ABC. Not natural in your sentence.
buat = “for” (colloquial/regional). Not typical on signs.

What exactly does tunai mean? Other ways to say it?

tunai = cash, in the sense of “paid in cash/on the spot.” Other expressions:
wang tunai = cash (money)
secara tunai = in cash (adverbial): membayar secara tunai
Opposite idea: tanpa tunai = cashless In Indonesian contexts you might also see kontan.

Does kaunter itu mean one counter or more?

Malay doesn’t mark plural by default, so it depends on context. To be explicit:

Singular: kaunter itu
Plural: kaunter-kaunter itu or kaunter-kaunter tersebut (“those said counters”)

How formal is this sentence? What would a casual version look like?

It’s neutral–formal, perfect for signs. Colloquial alternatives:

Kaunter ni tunai je. (ni = ini “this”, je = sahaja)
Kaunter ni cash je. (code-mixed with English)
Kaunter ini untuk tunai saja. (still fairly standard)

Are there shorter versions I might see on a sign?

Yes, common concise variants include:

Kaunter tunai sahaja
Bayaran tunai sahaja
Tunai sahaja They’re elliptical but readily understood.

How do I say “not only cash (but also cards)”?

Use bukan (hanya) … sahaja, followed by tetapi/namun juga:

Kaunter itu bukan hanya untuk bayaran tunai sahaja; kad juga diterima.
Kaunter itu bukan untuk bayaran tunai sahaja; pembayaran dengan kad turut diterima.

Any quick pronunciation tips?

kaunter: “KOWN-ter” (au like “cow”)
itu: “EE-too”
hanya: “HAN-yah” (h is pronounced)
untuk: “OON-tooʔ” (final k is a glottal stop)
bayaran: “bah-YAH-rahn”
tunai: “too-NIGH” Malay stress is light, often near the penultimate syllable.

Are there near-synonyms to sound more formal or explicit?

Kaunter itu khusus untuk bayaran tunai. (specifically for)
Kaunter itu terhad kepada bayaran tunai. (limited to)
Noun-phrase style: Kaunter bayaran tunai sahaja. (Payment counter—cash only)

Is this phrasing also used in Indonesian? Any differences?

It’s understandable across Malay/Indonesian, but Indonesian signage might prefer:

Loket ini hanya untuk pembayaran tunai. (loket = counter/ticket window)
Kasir ini hanya menerima tunai. (kasir = cashier) Indonesian also uses kontan for “cash” in some contexts; Malay favors tunai.