Rentestresstesten kontrollerer betjeningsevnen.

Because Norwegian very often builds compound nouns by joining words together.

• Rentestresstesten = rente
  • stress
    • test
      • definite ending
• betjeningsevnen = betjening
  • evne
    • definite ending

English often writes the same idea as several words, but Norwegian prefers one long noun. This is very normal and not considered unusual or overly formal.

They mark the nouns as definite singular, roughly like English the.

• rentestresstest = an interest stress test
• rentestresstesten = the interest stress test
• betjeningsevne = servicing ability / repayment ability
• betjeningsevnen = the servicing ability / the repayment ability

So Norwegian often puts the at the end of the noun instead of using a separate word.

Because nouns ending in -e often form the definite singular by adding just -n.

• evne → evnen
• jente → jenta/jenten depending on gender usage and style
• uke → uken/uka

So betjeningsevnen is perfectly regular: betjeningsevne + -n.

Kontrollerer is the present tense of å kontrollere.

Examples:

• jeg kontrollerer = I check
• du kontrollerer = you check
• den kontrollerer = it checks

In Norwegian, the present tense does not change according to the subject, so the same verb form is used for all persons.

Yes, here it means to check, to verify, or to inspect.

This is a very useful thing to know, because å kontrollere is a partial false friend for English speakers:

• sometimes it can mean control
• very often, especially in formal or technical language, it means check / verify

So in this sentence, kontrollerer is best understood as checks rather than controls.

This is the normal word order for a simple main clause:

subject + verb + object

• Rentestresstesten = subject
• kontrollerer = verb
• betjeningsevnen = object

This also fits the Norwegian V2 rule: in main clauses, the finite verb usually comes in the second position.

For example:

• Rentestresstesten kontrollerer betjeningsevnen.
• I banken kontrollerer rentestresstesten betjeningsevnen.

In both cases, the verb kontrollerer stays in second position.

It is a compound noun made from:

• betjening = servicing, handling, operation
• evne = ability, capacity

In financial language, betjeningsevne refers to the ability to service debt or manage required payments. So even if the literal parts look broad, the compound has a more specific meaning in this context.

This is common in Norwegian: a single compound noun can express an idea that English often translates with a longer phrase.

Because when a noun stands by itself, Norwegian usually shows definiteness with the ending on the noun itself:

• testen = the test
• evnen = the ability

A separate word such as den is usually added when there is an adjective:

• rentestresstesten = the interest stress test
• den grundige rentestresstesten = the thorough interest stress test

So in your sentence, no separate den is needed.