Questions & Answers about Jeg skal underrette banken.
Skal is the present tense of skulle, and in a sentence like this it usually expresses obligation, necessity, or a planned action.
So Jeg skal underrette banken can correspond to:
- I must notify the bank
- I have to notify the bank
- sometimes I’m supposed to notify the bank
Although shall is the traditional dictionary match, in modern English shall is often not the most natural translation. In real use, skal is often closer to must / have to / am going to, depending on context.
Because underrette comes after the modal verb skal.
After modal verbs in Danish—such as kan, vil, må, skal, bør—the next verb normally stays in the infinitive form:
- Jeg skal underrette banken
- Jeg vil underrette banken
- Jeg kan underrette banken
If you said underretter, that would be a finite present-tense verb, and then you would effectively have two fully conjugated verbs in the same simple clause, which is not how Danish works here.