Quote Originally Posted by oldboy
“This work has to be made at once.”

Why was "to be" used instead of "been"?
It is possible that "to be" is used in the capacity of "must" here... Am I right?
Yes, has to means must. The sentence means: the work must be finished immediately. (Has been means: the work is already finished.)

You can use other verbs (infinitives) with "has to" also:

He has to read the book = He must read the book.
She has to go shopping = She must (needs to) go shopping.

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Кстати, ваша "подпись" неправельно:
"I thank you for to correct me" should be: "I thank you for correcting me."

Or more simply: "Please correct me."