Tuj kiam mi ricevas la konteltiron, mi ĝin kontrolas.

Kiam means when.
Tuj means immediately or right away.

So tuj kiam means as soon as or the moment that. It adds the idea that the second action happens without delay.

• kiam mi ricevas... = when I receive...
• tuj kiam mi ricevas... = as soon as I receive...

Here the sentence sounds like a habit, routine, or general rule:

As soon as I receive the statement, I check it.

Esperanto often uses the present tense for that kind of repeated action.

If you wanted to talk about one specific future occasion, you could very naturally say:

Tuj kiam mi ricevos la konteltiron, mi ĝin kontrolos.

So:

• ricevas / kontrolas = habitual or general
• ricevos / kontrolos = one future event

The -n marks the direct object.

In this clause:

mi ricevas la konteltiron

the thing being received is la konteltiro, so it gets -n:

• la konteltiro = the account statement/account extract
• la konteltiron = the account statement/account extract as the direct object

The same idea appears in ĝin later:

• ĝi = it
• ĝin = it, as a direct object

So both konteltiron and ĝin are objects of their verbs.

It is a compound word, which is very common in Esperanto.

It is built from:

• konto = account
• eltiro = extract, excerpt, statement

Together, konteltiro means something like account statement or account extract.

Esperanto often combines ideas into a single word instead of using separate words. That is completely normal and one of the language’s most regular features.

La is the definite article, meaning the.

It shows that the speaker means a specific statement: the one they receive and then check.

Esperanto has:

• la = the
• no separate word for a/an

So la konteltiron means the account statement, not just any statement in general.

Both are grammatical.

• mi kontrolas ĝin
• mi ĝin kontrolas

Because Esperanto marks the object with -n, word order is more flexible than in English.

For many learners, mi kontrolas ĝin may feel more straightforward, because it matches normal English order more closely. But mi ĝin kontrolas is also perfectly valid. Putting ĝin before the verb can sound a bit more stylistic, emphatic, or simply natural to the speaker’s rhythm.

So this is mostly a word-order choice, not a change in basic meaning.

Yes, normally it is needed.

In the second clause, kontrolas is a transitive verb here, so if you mean I check it, Esperanto normally says the object explicitly:

mi ĝin kontrolas

If you said only:

mi kontrolas

that would mean just I check, with the object left unstated.

Since the speaker clearly means the statement, using ĝin is the normal way to refer back to it.

The comma separates the subordinate time clause from the main clause.

• Tuj kiam mi ricevas la konteltiron = subordinate clause
• mi ĝin kontrolas = main clause

This is very similar to English punctuation in sentences like:

As soon as I receive the statement, I check it.

So the comma helps show the structure of the sentence clearly.