Sprawdzę należność niezależnie od tego, czy wzrosła, czy spadła.

Because sprawdzę comes from the perfective verb sprawdzić. In Polish, perfective verbs do not normally have a true present tense. Their present-looking forms refer to the future.

So:

• sprawdzę = I will check
• sprawdzam = I am checking / I check from the imperfective sprawdzać

Here the speaker means a single completed act of checking, so sprawdzę is the natural choice.

Polish often leaves out subject pronouns when they are clear from the verb form.

• sprawdzę already means I will check
• so adding ja is usually unnecessary

You could say Ja sprawdzę..., but that would add emphasis, something like I will check.

Należność is a formal/business word. Depending on context, it can mean:

• amount due
• sum owed
• receivable
• sometimes more loosely payment due

It is not the most everyday word for money in general. It usually refers to a specific amount that is owed or payable.

Here it is the direct object of sprawdzę, so grammatically it is in the accusative.

However, with many feminine nouns ending in -ość, the nominative singular and accusative singular look the same:

• nominative: należność
• accusative: należność

So the form does not change, even though the case does.

As a fixed expression, niezależnie od tego means:

• regardless of that
• or, before a clause, regardless of whether

In this sentence, it introduces the idea that the checking will happen no matter which of two situations is true.

So niezależnie od tego, czy... is a very common pattern meaning regardless of whether...

Because the preposition od requires the genitive case.

The basic pronoun is to, and its genitive form is tego.

So:

• to = this/that/it
• od tego = of that / of it / regardless of that in this expression

In niezależnie od tego, czy..., tego points forward to the whole czy... clause.

This is the pattern czy..., czy..., which here means whether...or...

So:

• czy wzrosła, czy spadła = whether it increased or decreased

This is different from a simple or like lub or albo. After expressions like niezależnie od tego, zastanawiam się, nie wiem, and so on, Polish often uses czy to introduce alternatives.

Yes, it is the same word, but it has a different function here.

• In a yes/no question, czy can mean something like whether / is it the case that
• In this sentence, it is a subordinating conjunction, introducing alternatives inside a dependent clause

So a learner may recognize the same word, but the structure is different:

• Czy to prawda? = Is that true?
• Nie wiem, czy to prawda. = I don’t know whether it is true.
• ...czy wzrosła, czy spadła = ...whether it increased or decreased

Because they are past-tense feminine singular forms.

They refer to the omitted subject należność, which is a feminine noun.

So the logic is:

• należność is feminine singular
• therefore the verbs are feminine singular too:
  • wzrosła
  • spadła

If the subject were masculine, you would get forms like wzrósł or spadł.

Because the increase or decrease is viewed as happening before the future act of checking.

The meaning is basically:

• I will check the amount due, regardless of whether it has gone up or gone down

Also, Polish past tense often covers what English expresses with either:

• simple past: increased / decreased
• or present perfect: has increased / has decreased

So wzrosła and spadła are normal here.

Because wzrosła and spadła are perfective and describe a completed change:

• wzrosła = went up / has increased
• spadła = went down / has decreased

By contrast, rosła and spadała are imperfective and suggest an ongoing process, repeated movement, or background description:

• rosła = was increasing
• spadała = was decreasing

Here the sentence is about the result of the change, not the process, so the perfective forms fit better.

Because Polish often omits repeated elements when they are easy to understand from context.

A fuller version would be:

Sprawdzę należność niezależnie od tego, czy należność wzrosła, czy spadła.

But repeating należność sounds unnecessary. Once the noun has been mentioned, the later verbs can stand alone, and the listener understands that należność is still the subject of that clause.

Yes, in standard Polish punctuation they are expected.

You have:

Sprawdzę należność niezależnie od tego, czy wzrosła, czy spadła.

The commas mark:

• the start of the subordinate czy clause
• the separation between the two alternatives: czy wzrosła, czy spadła

So the punctuation is normal and standard.