Við teljum ekki fram í ljósi þess að launamiðinn er rangur.

Because við means we, and the verb has to match that subject.

• The infinitive is að telja = to count / to declare / to report.
• The present-tense form for við (we) is teljum.

So:

• ég tel = I count
• þú telur = you count
• við teljum = we count

The ending -um is a very common present-tense ending for we in Icelandic.

In a normal Icelandic main clause, ekki usually comes after the finite verb.

So the structure is:

• Við teljum ekki ...
• literally: We count not ...

That may feel different from English, where we say we do not count / we are not declaring, but it is normal Icelandic word order.

Compare:

• Ég skil ekki. = I do not understand.
• Hún kemur ekki. = She is not coming.
• Við teljum ekki fram. = We are not filing / reporting.

Telja fram is a fixed expression, so you should learn it as a unit.

While telja by itself often means count, the phrase telja fram has a more specific meaning such as:

• declare
• report
• file, especially in financial or tax contexts

So fram is not just a random extra word. It helps create the idiomatic meaning of the whole phrase.

This is common in Icelandic: a verb plus a small particle can have a meaning that is not identical to the basic verb alone.

Í ljósi þess að is a set phrase meaning:

• in light of the fact that
• more naturally in English: since, because, or given that

It is quite formal in tone.

Breakdown:

• í = in
• ljósi = light (in the dative form here)
• þess = that / it / this, in a grammatical form required by the expression
• að = that

So literally it is something like in light of that that..., but you should treat í ljósi þess að as one whole connector introducing a reason.

Yes, often it could, but the tone changes a little.

• vegna þess að = because
• í ljósi þess að = in light of the fact that / given that

So í ljósi þess að sounds a bit more formal, official, or careful.

Compare:

• Við teljum ekki fram vegna þess að launamiðinn er rangur.
• Við teljum ekki fram í ljósi þess að launamiðinn er rangur.

Both can work, but the second sounds more formal or administrative.

Launamiðinn means the payslip.

The base noun is launamiði = payslip.
When Icelandic adds the definite article the to many nouns, it attaches it to the end of the word instead of using a separate word.

So:

• launamiði = a payslip
• launamiðinn = the payslip

That final -nn is the attached definite article in this form.

Also, launamiði is a masculine noun, and here it is in the nominative singular, because it is the subject of er rangur.

Because the adjective has to agree with the noun it describes.

The noun launamiðinn is:

• masculine
• singular
• nominative

So the adjective must also be:

• masculine
• singular
• nominative

That gives rangur = wrong / incorrect

Compare the three singular nominative forms:

• rangur = masculine
• röng = feminine
• rangt = neuter

Examples:

• bíllinn er rangur would use masculine
• bókin er röng uses feminine
• svarið er rangt uses neuter

Because after að in a subordinate clause, Icelandic normally keeps regular subject-verb order:

• að launamiðinn er rangur

That is different from the verb-second pattern you often see in main clauses.

So here:

• main clause: Við teljum ekki fram
• subordinate clause: að launamiðinn er rangur

A learner often notices that Icelandic word order changes in main clauses, but subordinate clauses are usually more straightforward.

Here í takes the dative case, which is why we get ljósi rather than the nominative ljós.

In Icelandic, some prepositions can take different cases depending on meaning. With í:

• accusative often suggests motion into something
• dative often suggests location or a fixed expression

In í ljósi þess að, the phrase is fixed, and ljósi is the correct dative form.

So this is a good example of something worth memorizing as a whole expression rather than trying to rebuild from scratch every time.

Here it is the conjunction that.

Icelandic að can do two different jobs:

• infinitive marker: to
  • að telja = to count
• conjunction: that
  • ég veit að... = I know that...
  • í ljósi þess að... = in light of the fact that...

In your sentence, it introduces a full clause:

• að launamiðinn er rangur = that the payslip is incorrect

So this is definitely the conjunction, not the infinitive marker.

It sounds somewhat formal, especially because of í ljósi þess að.

A more everyday way to express the reason might be:

• ... vegna þess að ... = because ...
• or sometimes even a simpler rewording depending on context

So the sentence feels suitable for:

• administrative writing
• workplace communication
• official explanations
• formal email language

The vocabulary itself is not extremely difficult, but the phrasing is more formal than casual conversation.