Wpisuję numer IBAN i tytuł przelewu.

Pisać means to write in a general sense.
Wpisywać means to write/enter something into a specific place.

So in a banking or form-filling context, wpisuję is the natural choice because you are entering data into fields.

Wpisuję is:

• 1st person singular
• present tense
• imperfective

So it means I am entering or I enter, depending on context.

The ending -ę shows that the subject is I.

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

So:

• Wpisuję numer IBAN i tytuł przelewu. = normal, neutral
• Ja wpisuję numer IBAN i tytuł przelewu. = more emphatic, like I am the one entering it

Not with the same meaning.

• wpisuję = I am entering / I enter
• wpiszę = I will enter

Wpiszę is perfective and usually refers to a completed future action, not a present one.

Because numer is the direct object of the verb wpisuję.

In Polish, masculine inanimate nouns often have the same form in the nominative and accusative singular.
So:

• nominative: numer
• accusative: numer

That is why the sentence has wpisuję numer.

Often IBAN stays unchanged, especially in phrases like numer IBAN.

You may also hear forms like IBAN-u in some contexts, especially in more natural everyday usage when speakers add a Polish ending to the acronym. But in this sentence, numer IBAN is completely normal.

Grammatically, it is a noun phrase meaning literally title of the transfer.

In banking English, it is usually something like:

• payment reference
• transfer title
• description
• reference line

So tytuł przelewu is not really a “title” in the book-title sense. It is the text attached to the bank transfer.

Because Polish uses the genitive to express of very often.

So:

• tytuł = title
• przelew = transfer
• tytuł przelewu = title/reference of the transfer

The base form is przelew, but after tytuł it becomes przelewu.

Polish does not have articles like a, an, or the.

So numer IBAN can mean:

• an IBAN number
• the IBAN number

and tytuł przelewu can mean:

• a transfer title
• the transfer title

The exact meaning depends on context.

No, Polish word order is fairly flexible.

The original order is neutral and natural:

• Wpisuję numer IBAN i tytuł przelewu.

But other orders are possible, for example:

• Wpisuję tytuł przelewu i numer IBAN.

That would still be correct; it would just present the items in a different order.