Learn Hardcore Ukrainian: Незважаючи на невеликий платіж, банк перевіряє підозрілу операцію. - Despite the small payment, the bank is checking the suspicious transaction.

Yes. Literally, незважаючи comes from a verb meaning not looking / not paying attention, so word-for-word незважаючи на is something like without looking at.

But in modern Ukrainian, this expression is very commonly used idiomatically to mean:

despite
in spite of

So in this sentence, Незважаючи на невеликий платіж... means Despite the small payment...

It functions like a fixed expression, so learners usually just remember незважаючи на + accusative.

Why is невеликий платіж in that form after незважаючи на?

Because незважаючи на takes the accusative case.

So the noun phrase after it must be accusative:

невеликий платіж = a small payment

Here, both words look the same as the nominative form, but that is normal because:

платіж is a masculine inanimate noun
in the singular, masculine inanimate nouns often have the same nominative and accusative form
the adjective невеликий also matches that pattern here

So although it looks like nominative, grammatically it is accusative because of незважаючи на.

Why is there a comma after ?