I henhold til underretningen vurderer klageinstansen klagen.

I henhold til is a fixed, formal expression meaning according to, in accordance with, or pursuant to.

A few important points:

• It is best learned as a whole phrase.
• Henhold is not a very common everyday noun on its own.
• This expression is especially common in legal, administrative, and official Norwegian.

So in this sentence, i henhold til underretningen means something like according to the notification or in accordance with the notification.

This is because of the Norwegian V2 rule: in a main clause, the finite verb normally comes in second position.

Here, the first element is the whole prepositional phrase:

I henhold til underretningen

Because that phrase comes first, the verb must come second:

I henhold til underretningen vurderer klageinstansen klagen.

So the structure is:

• first element: I henhold til underretningen
• finite verb: vurderer
• subject: klageinstansen
• object: klagen

If you put the subject first, the sentence becomes:

Klageinstansen vurderer klagen i henhold til underretningen.

That is also correct.

The parts are:

• klageinstansen = the subject
• vurderer = the verb
• klagen = the direct object

So:

• the appeals body / complaints authority is doing the action
• assesses / considers is the action
• the appeal / complaint is what is being assessed

The opening phrase I henhold til underretningen is an adverbial phrase giving the basis or source.

Klageinstansen is a compound noun:

• klage = complaint / appeal
• instans = body, authority, instance, level
• -en = the definite singular ending

So en klageinstans means an appeals body or a complaints authority, and klageinstansen means the appeals body.

In official contexts, this usually refers to the body that handles or reviews appeals.

Because Norwegian usually puts the definite article at the end of the noun instead of using a separate word like the.

Examples:

• en underretning = a notification

• underretningen = the notification

• en klage = a complaint / an appeal

• klagen = the complaint / the appeal

• en klageinstans = an appeals body
• klageinstansen = the appeals body

So the ending -en here marks definite singular for nouns of common gender.

Because Norwegian usually expresses definiteness with a suffix attached to the noun.

English:

• the complaint
• the notification

Norwegian:

• klagen
• underretningen

This is one of the biggest structural differences from English. Instead of a separate article before the noun, Norwegian often adds the article to the end.

Underretning means something like notification, notice, or formal information.

It is a fairly formal word. In everyday speech, people are more likely to use words like:

• beskjed = message / notice / information
• melding = message / notice
• varsel = warning / notice

So underretningen sounds official, bureaucratic, or legal rather than conversational.

It can mean either, depending on context.

In legal and administrative Norwegian, klage often means appeal: a formal challenge to a decision.

That is especially likely here because of the word klageinstansen, which is typically an authority that handles appeals.

So although klage can be translated as complaint, in this kind of official sentence appeal may be the better interpretation.

Vurderer is the present tense of å vurdere, meaning to assess, to consider, or to evaluate.

In Norwegian official language, the present tense is often used to describe:

• current actions
• standard procedures
• formal statements of what an authority does

So vurderer can sound like:

• assesses
• is assessing
• sometimes even will assess, depending on context

If the sentence had skal vurdere, that would more clearly mean will assess or is to assess.

Yes. A very natural alternative is:

Klageinstansen vurderer klagen i henhold til underretningen.

This has the same basic meaning.

The difference is mostly about emphasis and information structure:

• I henhold til underretningen vurderer klageinstansen klagen
  puts early focus on the basis or source

• Klageinstansen vurderer klagen i henhold til underretningen
  starts more directly with the subject

Both are grammatical.

They can overlap, but they are not always identical.

• ifølge usually means according to or as stated by
• i henhold til usually means in accordance with, under, or pursuant to

So i henhold til often sounds a bit more formal and can suggest following a rule, document, or official basis.

Compare:

• Ifølge underretningen ... = according to the notification
• I henhold til underretningen ... = in accordance with / pursuant to the notification

In many contexts both are possible, but i henhold til is especially typical in legal or bureaucratic language.

It is grammatical and natural, but it sounds formal and administrative, not conversational.

Words and phrases that make it formal include:

• i henhold til
• underretningen
• klageinstansen
• vurderer klagen

In everyday speech, a speaker might choose simpler wording. For example, they might use more common vocabulary and a less official structure.

So this sentence is exactly the kind of Norwegian you might see in letters from authorities, legal texts, or formal decisions.