Mi kontrolis la saldon sen ke mi uzis konteltiron.

It is understandable, but many speakers would probably choose a more natural form:

Mi kontrolis la saldon sen uzi konteltiron.

Because the subject is the same in both parts, Esperanto often prefers sen + infinitive (sen uzi) rather than sen ke + a full clause.

If you do keep sen ke, many speakers would prefer sen ke mi uzu konteltiron rather than sen ke mi uzis konteltiron.

The ending -is marks the past tense in Esperanto.

So:

• kontrolas = check / am checking
• kontrolis = checked
• kontrolos = will check

In this sentence, the checking happened in the past, so kontrolis is used.

The -n marks the direct object.

Here, la saldon is the thing that was checked:

• Mi kontrolis = I checked
• la saldon = the balance

So saldo becomes saldon because it is receiving the action of kontrolis.

sen means without.

When sen is followed by a whole clause with its own subject and verb, Esperanto can use sen ke:

• sen ke mi uzu... = without me using...
• more literally: without it being the case that I use...

That said, when the subject is the same as in the main clause, Esperanto often prefers the simpler infinitive construction:

• sen uzi konteltiron = without using an account statement

So sen ke is possible in principle, but often not the most natural choice here.

In this kind of sentence, uzu is often the better choice.

So many speakers would prefer:

Mi kontrolis la saldon sen ke mi uzu konteltiron.

Why? Because the clause after sen ke describes something that did not happen as part of the situation. Esperanto often uses -u in that kind of subordinate clause.

However, the best and most idiomatic version here is still probably:

Mi kontrolis la saldon sen uzi konteltiron.

So for a learner, sen uzi is the safest model to remember.

Because the sentence, as written, has two separate clauses:

• Mi kontrolis la saldon
• sen ke mi uzis/uzu konteltiron

Each clause normally states its own subject, so mi appears twice.

If you want to avoid repeating mi, that is another reason why sen uzi is nicer:

Mi kontrolis la saldon sen uzi konteltiron.

la is the definite article, meaning the.

So la saldon means the balance — a specific balance, presumably already known from context.

By contrast, konteltiron is just the tool or means involved, not a specific previously identified one, so no article is needed:

• sen uzi konteltiron = without using an account statement

If you wanted to make it definite, you could say la konteltiron, but that would mean a particular statement already known to the listener.

It is a compound word, based on:

• kont/o = account
• eltir/o = extract, statement

So konteltiro means something like account extract or account statement.

The final -n in konteltiron is there because it is the direct object of uzi.

Some speakers might also write kontoeltiro, which makes the parts easier to see. Either way, the idea is the same.

Because uzi is a transitive verb: you use something.

So in:

• mi uzis konteltiron
• mi uzu konteltiron
• sen uzi konteltiron

the word konteltiron is the direct object of uzi, so it takes -n.

That means the sentence contains two direct objects in two different parts:

• la saldon = object of kontrolis
• konteltiron = object of uzis / uzu / uzi