Mva-meldingen er ferdig, bortsett fra at ett bilag mangler.

Mva stands for merverdiavgift, which is Norwegian for VAT (value-added tax).

So Mva-meldingen means the VAT return or the VAT report, depending on context.

• mva = VAT
• melding = message, report, return
• meldingen = the report/return

In business and accounting contexts, Mva-meldingen usually refers to the official VAT filing.

The hyphen is used because Mva is an abbreviation.

In Norwegian, abbreviations are often linked to another noun with a hyphen:

• mva-melding
• tv-serie
• it-avdeling

So Mva-meldingen is the normal written form for the VAT return.

Because Norwegian often attaches the definite article to the end of the noun.

• en melding = a message/report
• meldingen = the message/report

So:

• mva-melding = a VAT return
• mva-meldingen = the VAT return

This is one of the most important features of Norwegian nouns: the is often added as a suffix rather than written as a separate word.

Er ferdig means is finished, is done, or is ready.

In this sentence, Mva-meldingen er ferdig means that the VAT return is basically complete.

A few examples:

• Jeg er ferdig. = I’m done.
• Rapporten er ferdig. = The report is finished.
• Vi er ferdige med arbeidet. = We are finished with the work.

Here, ferdig describes the state of the VAT return.

Bortsett fra at means except that or apart from the fact that.

So:

• Mva-meldingen er ferdig, bortsett fra at ett bilag mangler. = The VAT return is finished, except that one receipt/document is missing.

This phrase is useful when something is mostly true, but there is one exception.

Compare:

• bortsett fra regnet = except for the rain
• bortsett fra at det regner = except that it’s raining

So bortsett fra can be followed by:

• a noun phrase: bortsett fra ett bilag
• a clause with at: bortsett fra at ett bilag mangler

Because after at, Norwegian uses normal subordinate-clause word order: subject + verb.

So:

• ett bilag = subject
• mangler = verb

That gives:

• at ett bilag mangler

This is different from main clauses, where Norwegian often has verb-second word order.

Compare:

• Ett bilag mangler. = One document is missing.
• Nå mangler ett bilag. = Now one document is missing.
• ...at ett bilag mangler. = ...that one document is missing.

After at, you do not move the verb to second position in the same way as in a main clause opening with another element.

Because bilag is a neuter noun in Norwegian.

Norwegian indefinite articles depend on grammatical gender:

• en for many masculine/feminine nouns
• et for neuter nouns

So:

• et bilag = a document / voucher / receipt attachment

When stressed or when standing alone in some contexts, et can appear as ett. That is what happens here:

• ett bilag mangler = one document is missing

Here ett emphasizes the number one a bit more clearly.

In everyday Norwegian, bilag can mean an attachment or supporting document.

In accounting, it usually means a voucher, receipt, supporting document, or accounting document.

So in this sentence, ett bilag mangler means that one supporting financial document has not been included or cannot be found.

Depending on context, a natural English translation could be:

• one receipt is missing
• one voucher is missing
• one supporting document is missing

Mangler means is missing, is lacking, or is absent.

It comes from the verb å mangle.

Examples:

• Det mangler en side. = A page is missing.
• Vi mangler informasjon. = We lack information.
• Hun mangler erfaring. = She lacks experience.

In your sentence:

• ett bilag mangler = one supporting document is missing

So the idea is that the VAT return is complete, but one necessary document is still not there.

Yes, that is possible, but the meaning is slightly different in nuance.

• bortsett fra at ett bilag mangler = the VAT return is finished, except that one document is missing
• bortsett fra ett bilag = finished except for one document

The version with at + clause sounds a bit fuller and more explicit, because it clearly states what the problem is: the document is missing.

The shorter noun version is also natural, but it is a little more compact and less explicit.