Ich nenne die Kontoverbindung, denn sie ist für die Auszahlung nötig.

Because die Kontoverbindung is the direct object of nennen in this sentence.

• Ich = subject
• nenne = verb
• die Kontoverbindung = thing being named/stated/provided

The verb nennen usually takes an accusative object, and Kontoverbindung is a feminine noun, so its accusative singular form is die Kontoverbindung.

So here:

• nominative: die Kontoverbindung
• accusative: die Kontoverbindung

For this noun, nominative and accusative look the same.

Literally, nennen often means to name or to call. But in this sentence, it is being used more like:

• to state
• to give
• to provide
• to mention

So Ich nenne die Kontoverbindung means something like I provide/state the bank details.

This is a good example of how a German verb may have a broader range than its most basic dictionary meaning.

Kontoverbindung usually means bank account details or banking details.

It is a compound noun:

• Konto = account
• Verbindung = connection/link

In real usage, it refers to the information needed for a payment or transfer, such as:

• account number
• IBAN
• BIC
• bank details generally

So even though the word is singular, in English it is often translated with a plural idea like bank details.

Here denn means because.

So:

• Ich nenne die Kontoverbindung, denn sie ist für die Auszahlung nötig.
• I provide the bank details, because they are necessary for the payout.

The important grammar difference is:

With denn

It is a coordinating conjunction, so normal main-clause word order stays the same.

• ..., denn sie ist für die Auszahlung nötig.
• subject sie
  • verb ist

With weil

It is a subordinating conjunction, so the verb goes to the end.

• ..., weil sie für die Auszahlung nötig ist.

So both can mean because, but the word order is different.

Because denn links two main clauses, and in German that is normally separated by a comma.

The two clauses are:

1. Ich nenne die Kontoverbindung
2. sie ist für die Auszahlung nötig

When joined with denn, you write:

• Ich nenne die Kontoverbindung, denn sie ist für die Auszahlung nötig.

So the comma is standard punctuation here.

Sie refers to die Kontoverbindung.

Since Kontoverbindung is:

• singular
• feminine

the matching pronoun is sie.

So here sie means it, not she and not they.

German uses grammatical gender, so a feminine noun is often referred to with sie, even when English would simply use it.

Because für always takes the accusative case.

The noun is die Auszahlung (feminine), and in the accusative singular it is still die Auszahlung.

So:

• für
  • accusative
• für die Auszahlung = for the payout/payment

This is a very useful rule to memorize:

• für + accusative always

Auszahlung means payout, payment, or disbursement, depending on context.

It comes from the verb auszahlen, which means to pay out.

So für die Auszahlung nötig means:

• necessary for the payout
• necessary in order for the money to be paid out

In practical contexts, this often refers to money being transferred to someone.

Because nötig is a predicate adjective linked to ist.

In the clause:

• sie ist für die Auszahlung nötig

the finite verb ist must be in the second position, and the rest of the information follows. The adjective nötig comes near the end as part of the predicate.

You can think of it as:

• sie = subject
• ist = verb
• für die Auszahlung = prepositional phrase
• nötig = adjective describing the subject

This word order is natural in German. English also often puts the adjective after to be:

• it is necessary

German just allows the other phrase to come before the adjective:

• sie ist für die Auszahlung nötig

Yes. Nötig and notwendig both mean necessary.

So you could also say:

• Ich nenne die Kontoverbindung, denn sie ist für die Auszahlung notwendig.

The meaning is basically the same. In many contexts:

• nötig sounds a bit more everyday
• notwendig can sound slightly more formal or emphatic

But both are correct here.