Platna transakcija je na izvodu sa računa.

Here platna means payment-related or used for payments. It is an adjective modifying transakcija, so platna transakcija means payment transaction.

This is a fairly formal/banking-style expression, not very casual everyday speech.

Because it agrees with transakcija, which is:

• feminine
• singular
• nominative (the subject of the sentence)

So the adjective must match it:

• platni — masculine
• platna — feminine
• platno — neuter

Since transakcija is feminine, Serbian uses platna.

It is in the nominative singular.

That is because it is the subject of the sentence:

• Platna transakcija = the thing being talked about
• je = is
• na izvodu sa računa = on the bank statement

So the basic structure is:

[subject] + [is] + [location]

Je is the 3rd person singular present tense of biti (to be), so it means is.

In this sentence, it links the subject to its location:

• Platna transakcija = the payment transaction
• je = is
• na izvodu sa računa = on the bank statement

In standard Serbian, you normally keep je in a sentence like this. Omitting it would sound incomplete except in very special contexts such as headlines or notes.

Izvodu is in the locative singular.

That is because the preposition na can take different cases depending on meaning, and here it expresses location:

• na izvodu = on the statement

With location, na usually takes the locative.

So:

• nominative: izvod
• locative singular: izvodu

Računa is in the genitive singular.

The phrase izvod sa računa is a standard banking expression meaning statement from the account, which in natural English is bank statement or account statement.

So:

• račun = account
• sa računa = from the account

In this phrase, sa means something like from/off, and it is followed by the genitive.

Because they do two different jobs:

• na izvodu = on the statement
  
  • this tells you where something appears
• sa računa = from the account
  
  • this tells you what kind of statement it is

So the whole phrase means:

• on the statement
• specifically, the statement from the account

In better English: on the bank statement

Here it means account, specifically a bank account.

The word račun can mean different things depending on context, including:

• account
• bill
• invoice
• calculation

But in the fixed expression izvod sa računa, it means account, so the full phrase means account statement / bank statement.

Usually na izvodu is the more natural choice here.

That is because Serbian often uses na for something appearing on a document, page, list, statement, screen, and similar surfaces or records.

So in banking language:

• na izvodu sa računa = the natural phrase for on the bank statement

U izvodu is not impossible in some broader sense of in the extract/excerpt, but for this banking meaning, na izvodu is what learners should expect.

Because Serbian does not have articles like English a and the.

So Platna transakcija can mean:

• a payment transaction
• the payment transaction

Which one is meant depends on context.

In this sentence, context would tell you whether English should use a or the.

Yes. Serbian word order is more flexible than English word order.

The sentence as given is a neutral, straightforward version:

• Platna transakcija je na izvodu sa računa.

But you could also move things around for emphasis, for example:

• Na izvodu sa računa je platna transakcija.

That sounds more like emphasizing where it is.

Still, the original order is a very normal one for learners to use.

Yes, it is natural, especially in a formal, banking, or administrative context.

A few other natural variants are:

• Platna transakcija se nalazi na izvodu sa računa.
• Transakcija je prikazana na izvodu sa računa.
• Platna transakcija je evidentirana na izvodu sa računa.

These sound a bit more official or descriptive. The original sentence is short, clear, and perfectly acceptable.