Snabdevač i potrošač su proverili račun.

In Serbian, the past tense is usually made with:

• the present tense of biti (to be)
  +
• the l-participle of the main verb

So here:

• su = they are / auxiliary part of the past tense
• proverili = past participle form of proveriti (to check, verify)

Together, su proverili means checked.

This is very common in Serbian:

• Ja sam video = I saw
• Oni su došli = They came
• Mi smo pročitali = We read / have read

So Snabdevač i potrošač su proverili račun literally has the structure Supplier and consumer are checked bill, but naturally means The supplier and the consumer checked the bill/account.

Because the subject has two people/things joined by i (and):

• snabdevač = supplier
• potrošač = consumer

Together, they form a plural subject, so the verb must also be plural.

That is why Serbian uses:

• su = plural auxiliary
• proverili = plural masculine/mixed-gender past participle

If there were only one subject, you would get singular:

• Snabdevač je proverio račun. = The supplier checked the bill/account.
• Potrošač je proverio račun. = The consumer checked the bill/account.

The ending -ili marks the masculine plural form of the past participle.

Serbian past participles agree with the subject in gender and number. For example:

• proverio = masculine singular
• proverila = feminine singular
• proverilo = neuter singular
• proverili = masculine plural or mixed-gender plural
• proverile = feminine plural

Since snabdevač and potrošač are masculine nouns, the sentence uses proverili.

Even if the group were mixed male and female, Serbian normally still uses the masculine plural form.

They are in the nominative case, because they are the subject of the sentence.

You can tell they are the ones doing the action of checking.

• snabdevač = the supplier
• potrošač = the consumer

In Serbian, the nominative is the basic dictionary form of a noun and is commonly used for the subject.

Račun is in the accusative case, because it is the direct object — the thing that was checked.

However, for many masculine inanimate nouns in Serbian, the accusative singular looks exactly the same as the nominative singular.

So:

• nominative: račun
• accusative: račun

That is normal.

Compare that with a masculine animate noun, where nominative and accusative are often different:

• nominative: student
• accusative: studenta

But with račun, there is no visible change.

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

So snabdevač, potrošač, and račun can mean:

• a supplier
• the supplier
• a consumer
• the consumer
• a bill/account
• the bill/account

Which one is meant depends on context.

So in this sentence, English may translate it as:

• The supplier and the consumer checked the bill or
• A supplier and a consumer checked an account

The surrounding context tells you which is most natural.

I means and.

It joins the two nouns:

• snabdevač i potrošač = the supplier and the consumer

It is a very common Serbian conjunction.

Be careful not to confuse Serbian i with English I. Serbian i is pronounced like English ee.

Račun can mean several related things, depending on context:

• bill or invoice
• receipt in some contexts
• account
• calculation

In this sentence, without more context, račun could reasonably mean:

• bill/invoice
• account

A learner should know that Serbian often uses one word where English uses several different words.

So the exact translation depends on the situation:

• in a shop or restaurant: probably bill
• in finance/business: possibly account or invoice

In Serbian, short unstressed words such as auxiliary forms often behave like clitics. These words usually appear near the beginning of the clause, often in the second position.

That is why you get:

• Snabdevač i potrošač su proverili račun.

The auxiliary su comes after the subject phrase Snabdevač i potrošač.

This placement is very typical in Serbian.

For example:

• Oni su došli. = They came.
• Marija i Ivan su stigli. = Marija and Ivan arrived.

You generally should not place su randomly; clitic placement follows regular patterns in Serbian.

Proveriti is perfective.

That means it presents the action as a completed whole: to check / to verify completely.

Its imperfective partner is usually proveravati or sometimes proverati in certain usage patterns, but proveravati is the common learner-friendly pair.

So:

• proveriti = to check once, to verify, to finish checking
• proveravati = to be checking, to check repeatedly/habitually

In this sentence, su proverili suggests a completed action:

• They checked it / They have checked it

That is why the perfective verb fits naturally.

Yes, Serbian word order is more flexible than English word order, although not completely free.

The neutral order here is:

• Snabdevač i potrošač su proverili račun.

But other orders are possible for emphasis or style, for example:

• Račun su proverili snabdevač i potrošač.
  = It was the bill/account that the supplier and the consumer checked.

This shifts focus toward račun.

However, for learners, it is best to start with the neutral pattern: subject + auxiliary + main verb + object

A rough guide for an English speaker:

• snabdevač ≈ snahb-DEH-vach
• potrošač ≈ poh-TROH-shach
• račun ≈ RAH-choon

A few useful pronunciation points:

• č sounds like ch in church
• š sounds like sh in shoe
• ć and č are different sounds in Serbian, but beginners often first learn č as a clear ch
• Serbian spelling is very phonetic, so words are usually pronounced as written

Yes, these are grammatically masculine singular nouns.

You can often recognize masculine nouns in Serbian because many of them end in a consonant, as these do:

• snabdevač
• potrošač

That grammatical gender matters because it affects agreement, including the past participle:

• snabdevač je proverio
• potrošač je proverio

And with both together:

• snabdevač i potrošač su proverili

Yes. Serbian past tense does not map perfectly onto the English difference between checked and have checked.

Su proverili can often be translated as:

• checked
• have checked

The best English choice depends on context.

So the Serbian form is one past tense form, while English may choose between different past constructions.