Learn Dutch: Moet ik het formulier nu invullen? - Do I have to fill in the form now?

In Dutch, moeten means both 'must' and 'to have to'. English speakers often say 'do I have to' for questions because 'must I' sounds very formal, but in Dutch, moet ik is the standard, everyday way to ask about an obligation.

Why are the verbs moet and invullen separated by the rest of the sentence?

When you use a modal verb like moeten (must/have to), it takes the normal verb position. Because this is a yes/no question, it goes at the very beginning. The main action verb, invullen (to fill in), gets pushed to the very end of the sentence in its full dictionary form (the infinitive).

Since the full verb is moeten, why is the word here just moet?

Moet is the conjugated form used for singular subjects like ik (I), jij (you), and hij/zij/het (he/she/it). Because the subject here is ik, you use moet.

I thought invullen was a separable verb. Why is it written as one word here?