No revisamos el saldo pendiente, sino el finiquito.

It can mean either one. With -ar verbs, the nosotros form is the same in the present indicative and the preterite:

• revisamos = we review / we are reviewing
• revisamos = we reviewed

Only context tells you which tense is meant.

This structure is used to correct or replace the first idea after a negative statement. It means not X, but Y.

So here, the sentence is saying that the thing reviewed was not the first item mentioned, but the second one.

Because sino is used when the second part replaces the first one after a negation.

• No revisamos el saldo pendiente, sino el finiquito.
  = We reviewed not the outstanding balance, but the settlement.

By contrast, pero gives general contrast, not this kind of direct correction. So sino is the right choice here.

Use sino when it is followed by a noun, adjective, or phrase. Here it is followed by el finiquito, which is a noun phrase.

Use sino que when it is followed by a full clause with a conjugated verb.

Compare:

• No revisamos el saldo pendiente, sino el finiquito.
• No revisamos el saldo pendiente, sino que revisamos el finiquito.

Both are grammatical, but the first is more concise and more natural here.

A comma is normally used before sino in this kind of contrast. It helps separate the rejected idea from the corrected one:

• not the outstanding balance, but the settlement

It makes the contrast clearer and is the standard punctuation.

In Spanish, adjectives often come after the noun, especially when they describe a category or type. Here pendiente is specifying what kind of saldo it is: an outstanding or unpaid balance.

So saldo pendiente is the normal order.

Here pendiente means outstanding, unpaid, or still unresolved. In financial or administrative language, it often refers to something that is still owed or still needs to be dealt with.

So it is a very common adjective in business and finance Spanish.

In Spain, finiquito usually refers to the final settlement when a job or contract ends. It can include things like:

• unpaid salary
• unused holiday pay
• extra payments still owed

It can also refer to the document that records that final settlement. It is a very common Spain-specific employment term.

Spanish often uses the definite article when referring to specific things understood from the context. Here, el saldo pendiente and el finiquito are treated as identifiable items.

Keeping the article before both nouns also makes the contrast more balanced and natural.

Because Spanish often avoids repeating words that are already clear from the context. After sino, the verb revisamos is understood, so it does not need to be repeated.

That is why:

• No revisamos el saldo pendiente, sino el finiquito.

is more natural than repeating the whole structure again.