Taksa je plaćena.

Not exactly.

• taksa usually means a fee, charge, or official administrative payment
• porez means tax

So taksa is often something like a court fee, processing fee, registration fee, or similar official charge, not a general tax.

Taksa is in the nominative singular.

Why?

• It is the grammatical subject of the sentence.
• The sentence is saying something about the fee: The fee is/has been paid.

The basic dictionary form is also taksa, so here the nominative and dictionary form are the same.

Because plaćena must agree with taksa.

Taksa is:

• feminine
• singular
• nominative

So the participle/adjectival form must also be:

• feminine
• singular
• nominative

That gives plaćena.

Compare:

• račun je plaćen = the bill is/has been paid
• taksa je plaćena = the fee is/has been paid
• pismo je plaćeno = the letter/postage is/has been paid

Je is the 3rd person singular present form of biti = to be.

So:

• taksa = fee
• je = is
• plaćena = paid

Together, je + plaćena forms a passive/resultative-style meaning: the fee is in the state of being paid.

In natural English, this often corresponds to:

• The fee has been paid
• sometimes The fee is paid

depending on context.

Yes, effectively it is.

Serbian often uses biti + passive participle to express something like an English passive:

• Taksa je plaćena. = The fee has been paid.

The focus is not on who paid it, but on the result.

If you wanted to mention the person, you would usually rephrase the sentence rather than simply adding an English-style by phrase.

It can correspond to both, but in many real situations the most natural English translation is:

• The fee has been paid.

Why? Because the Serbian sentence often emphasizes the completed result: the payment is already done.

So in official or practical contexts, has been paid is usually the best match.

It comes from the verb platiti = to pay.

Plaćena is the passive participle (often taught as a kind of verbal adjective), and it agrees with the noun it describes.

Related forms:

• platiti = to pay
• plaćen = paid, masculine
• plaćena = paid, feminine
• plaćeno = paid, neuter
• plaćeni = paid, masculine plural

This is a very important difference.

• Taksa je plaćena = the fee has been paid / is already paid
• Taksa se plaća = the fee is paid, gets paid, or must be paid depending on context

So:

• je plaćena focuses on a completed result
• se plaća is more general, habitual, or sometimes instructional

For example:

• Taksa se plaća unapred. = The fee is paid in advance.
• Taksa je plaćena. = The fee has been paid.

Yes, and in many administrative contexts that is very common.

Difference in nuance:

• plaćena = paid
• uplaćena = paid in / transferred / deposited

Uplaćena often sounds a bit more specific and official, especially when money has been transferred to an account or submitted as a required payment.

So both can work, but uplaćena may sound more like a confirmed official payment transaction.

Yes.

The neutral order is:

• Taksa je plaćena.

But Serbian word order is flexible, so you may also see:

• Plaćena je taksa.

That version is more marked and may sound like it emphasizes paid or answer a question like What happened to the fee?

For a learner, Taksa je plaćena is the safest and most neutral version.

Roughly:

• pla-će-na

A very approximate English-style guide would be:

• PLAH-chyeh-nah

The important sound here is ć:

• ć is softer than č
• it is not exactly the English ch
• it is a distinctly Serbian sound, made farther forward and more softly

Also:

• je is pronounced roughly like yeh, not like English jee

So the whole sentence is approximately:

• TAK-sa yeh pla-će-na

In Cyrillic, it is:

• Такса је плаћена.

Serbian commonly uses both scripts:

• Latin: Taksa je plaćena.
• Cyrillic: Такса је плаћена.