Fakturanummeret står øverst.

Because Norwegian usually writes compound nouns as a single word.
So:

• faktura = invoice
• nummer = number
• fakturanummer = invoice number

This is very common in Norwegian. Where English often uses two words, Norwegian often uses one compound word.

The ending -et marks the noun as definite singular.

So:

• et fakturanummer = an invoice number
• fakturanummeret = the invoice number

Unlike English, Norwegian often adds definiteness to the end of the noun instead of using a separate word like the.

Because in Norwegian, definiteness is usually built into the noun itself.

In this sentence:

• fakturanummeret already means the invoice number

So you do not need a separate word before it.

Because nummer is a neuter noun in Norwegian, and compound nouns normally take the gender of the last part of the compound.

• et nummer
• therefore: et fakturanummer
• definite: fakturanummeret

Even though faktura is common gender, the whole compound follows nummer.

Norwegian often uses verbs like stå (stand), ligge (lie), and sitte (sit) to describe where something is located.

So står øverst literally suggests that the invoice number stands at the top. In natural English, this is usually just translated as is at the top.

This is very normal in Norwegian, especially when talking about text, objects, furniture, signs, and similar things.

Øverst means at the top or uppermost.

It is an adverb that describes position. In this sentence, it tells you where the invoice number is located.

Related forms:

• øverst = at the top / topmost
• øverste = top / uppermost, used before a noun
  Example: den øverste linjen = the top line

The word order is:

• Fakturanummeret = subject
• står = verb
• øverst = adverb of place/position

So the pattern is:

Subject + verb + adverb

This is the normal Norwegian main-clause order.

Yes. That is also correct.

When you move øverst to the front for emphasis, the verb still has to stay in second position in a main clause. This is the normal Norwegian V2 word order.

So:

• Fakturanummeret står øverst.
• Øverst står fakturanummeret.

Both are grammatical, but the second version gives more focus to øverst.

Yes, very common.

Norwegian often uses stå for information that appears in writing, on signs, in documents, or on screens.

For example:

• Navnet står øverst på siden. = The name is at the top of the page.
• Det står i brevet. = It says so in the letter.

So in this sentence, står sounds very natural.

A helpful approximation is:

fak-TU-ra-num-me-ret

A few useful points:

• the stress is mainly on tu
• r is pronounced in the Norwegian way, which varies by dialect
• u in faktura is not like English you
• the final -et is usually pronounced lightly

You do not need perfect pronunciation right away, but it helps to notice that long compound words are very common in Norwegian.

This sentence is standard Bokmål.

In Nynorsk, you would more likely see:

• Fakturanummeret står øvst.

The main difference here is øverst in Bokmål versus øvst in Nynorsk.