Račun je na stolu, ali ja još ne mogu da platim.

Yes — račun has several meanings, and context decides which one is intended.

Common meanings of račun include:

• bill / check in a restaurant or café
• account (for example, a bank account)
• calculation / math problem
• sometimes invoice

In Račun je na stolu, the natural meaning is the bill/check is on the table.

Je is a short form of biti (to be) and it behaves like a clitic in Serbian. Clitics usually go in the second position of the sentence or clause.

So:

• Račun je na stolu. = correct, natural
• The first unit is Račun, and je comes right after it.

This second-position rule is very common in Serbian and affects words like:

• je, sam, si, smo, ste, su
• short pronouns like ga, mu, mi, etc.

Because na stolu expresses location: the bill is on the table.

After na, Serbian can use different cases depending on meaning:

• na + accusative = movement toward a surface
  
  • Stavljam račun na sto. = I’m putting the bill onto the table.
• na + locative = location on a surface
  
  • Račun je na stolu. = The bill is on the table.

So:

• sto = accusative/nominative form
• stolu = locative singular

It is the locative singular of sto (table).

The pattern here is:

• na stolu = on the table

This is a very common locative use after prepositions of location such as:

• u = in
• na = on / at

Examples:

• u gradu = in the city
• na stolu = on the table

Yes, Serbian often drops subject pronouns because the verb already shows the person.

So you could say:

• ...ali još ne mogu da platim.

That would already mean ...but I still can’t pay.

Adding ja makes the subject more explicit and often gives:

• contrast
• emphasis

So ali ja još ne mogu da platim can sound like:

• but I still can’t pay
• but I can’t pay yet
• possibly with a slight contrast: but I can’t

Here još means still or yet, depending on how you translate it.

In this sentence:

• još ne mogu da platim = I still can’t pay / I can’t pay yet

The combination još + negative verb is very common for this idea.

Examples:

• Još ne znam. = I still don’t know / I don’t know yet.
• Još nije stigao. = He still hasn’t arrived / He hasn’t arrived yet.

In Serbian, negation is usually made with the separate particle ne placed before the verb.

So:

• mogu = I can
• ne mogu = I cannot / I can’t

This is normal:

• ne znam = I don’t know
• ne vidim = I don’t see
• ne mogu = I can’t

A learner should notice that Serbian writes this as two words in this case.

After verbs like moći (can), Serbian very often uses:

• da + present tense

So:

• mogu da platim = I can pay

This is one of the most common patterns in modern Serbian.

You may also encounter an infinitive in some contexts:

• mogu platiti

But mogu da platim is extremely natural and very common.

This is about aspect, which is very important in Serbian.

• platiti = perfective
  • to pay, as a completed act
• plaćati = imperfective
  • to be paying, to pay habitually, to pay in general

In this sentence, the speaker means a single completed payment of the bill, so the perfective verb is natural:

• ne mogu da platim = I can’t pay / I can’t complete the payment

If you said ne mogu da plaćam, it would suggest something more ongoing or repeated, like:

• I can’t be paying
• I can’t keep paying
• I’m unable to pay regularly

So for a restaurant bill, platim is the right choice.

Platim is the 1st person singular present tense form of platiti.

So:

• (ja) platim = I pay

But because it follows da, the whole phrase means:

• da platim = that I pay / to pay

In English we usually translate mogu da platim simply as:

• I can pay

Even though Serbian uses a present-tense form after da, the English translation is usually an infinitive.

Yes, in this sentence ali straightforwardly means but.

It connects two contrasting ideas:

• Račun je na stolu = The bill is on the table
• ali ja još ne mogu da platim = but I still can’t pay

So the contrast is:

• the bill is there,
• but the speaker still cannot pay.

Because Serbian does not have articles like a / an / the.

So:

• račun can mean a bill or the bill
• context tells you which one is meant

In this sentence, the natural English translation is the bill, because it is a specific bill already understood from the situation.

This is very common in Serbian:

• Knjiga je na stolu. = The book is on the table.
• Auto je ispred kuće. = The car is in front of the house.

Yes, Serbian word order is fairly flexible, but not completely free. Different word orders can change emphasis.

For example:

• Račun je na stolu, ali ja još ne mogu da platim. = neutral, natural
• Račun je na stolu, ali još ne mogu da platim. = also natural, less emphasis on ja
• Još ne mogu da platim. = emphasis on still/yet
• Ja još ne mogu da platim. = more emphasis on I

However, the clitic je still has to follow the normal clitic-placement rules, so you cannot move it just anywhere.

Depending on context, a very natural English sense would be:

• The bill is on the table, but I still can’t pay.
• The check is on the table, but I still can’t pay.
• The bill is on the table, but I can’t pay yet.

If this is in a restaurant, check may sound more natural in American English, while bill is also perfectly good and often more general.