Signaturkravet gjelder flyttemeldingen.

Because Norwegian usually writes compound nouns as a single word.

So:

• signatur = signature
• krav = requirement
• signaturkrav = signature requirement
• signaturkravet = the signature requirement

This is very common in Norwegian. English often uses two words where Norwegian uses one.

Examples:

• husdør = house door / front door
• passnummer = passport number
• flyttemelding = moving notification / change-of-address notice

The ending -et is the definite ending for a neuter noun.

The base noun is:

• et krav = a requirement

Definite form:

• kravet = the requirement

In the compound signaturkravet, the last part controls the gender and inflection. Since krav is neuter, the whole compound is also neuter:

• et signaturkrav = a signature requirement
• signaturkravet = the signature requirement

Gjelder is the present tense of å gjelde.

In this sentence, it means something like:

• applies to
• concerns
• is relevant for

So Signaturkravet gjelder flyttemeldingen means that the signature requirement applies to the moving notification.

Very often, å gjelde is used in official or administrative language.

Examples:

• Regelen gjelder alle. = The rule applies to everyone.
• Dette gjelder bare voksne. = This only applies to adults.

Because å gjelde can take a direct object in Norwegian.

So Norwegian says:

• gjelder flyttemeldingen

where English often prefers:

• applies to the moving notification

This is a normal difference between the two languages. You do not need a word corresponding to to here.

Compare:

• Loven gjelder alle ansatte. = The law applies to all employees.
• Unntaket gjelder ikke deg. = The exception does not apply to you.

Because flyttemelding is a common-gender noun, and -en marks the definite singular.

Forms:

• en flyttemelding = a moving notification
• flyttemeldingen = the moving notification

So in the sentence, it is referring to a specific moving notification, not just any moving notification.

The dictionary forms are:

• signaturkravet → signaturkrav
• gjelder → å gjelde
• flyttemeldingen → flyttemelding

More fully:

• et signaturkrav = a signature requirement
• å gjelde = to apply / concern
• en flyttemelding = a moving notification

Yes. This is standard Norwegian main-clause word order:

• Signaturkravet = subject
• gjelder = verb
• flyttemeldingen = object

So it follows the basic Subject – Verb – Object pattern.

If you move something else to the front, Norwegian usually makes the verb come second:

• For flyttemeldingen gjelder signaturkravet.
  This is less natural in most contexts, but it shows the verb-second rule.

The original sentence is the most neutral and natural version.

Yes. It is made from:

• flytte = to move
• melding = message / notice / notification

Together, flyttemelding means a notification that you have moved or are moving, often in an official administrative sense.

So Norwegian builds compounds very productively. That is why sentences like this can contain long nouns that are still completely normal.

Sometimes you may hear gjelder for, but in a sentence like this, gjelder flyttemeldingen is the cleaner and more standard phrasing.

So for a learner, the safest choice here is:

• Signaturkravet gjelder flyttemeldingen.

Using for is not always wrong in every context, but it is often unnecessary after å gjelde.

It sounds fairly formal or administrative.

That is mainly because of:

• signaturkravet
• gjelder
• flyttemeldingen

This is the kind of wording you might see on a government website, an official form, or an instruction page.

In everyday speech, people might use simpler wording depending on context, but this sentence is perfectly normal in formal written Norwegian.