Q:

Role of "be" in "Staff may request that a check be issued instead."

Staff may request that a check be issued instead.

I have two questions about this sentence.
First question:
I am not sure why "be" is used here.
Can anyone explain it, please?
Second question:
I made the following sentences to express the same meaning.
Are they correct?

Staff may request a check instead.
Staff may request a check to be issued instead.
Staff may request to issue a check instead.

A:

The construction { form of to be } + { past participle form of verb } is the passive voice.  It is a way of expressing an action without mentioning a specific person or category of people involved in the action, which can be used to be polite or businesslike, or to deflect blame.
Be is used instead of is because the phrase that a check be issued instead is in the subjunctive mood.  The subjunctive mood is confusing but it can appear after a number of verbs and request is one of those.
Your alternate sentences replace the that clause with a noun or verbal as an object of request, which is fine and 100% correct.  The subjunctive mood can be used to imply politeness, business politeness, or formality, and this is lost when you "convert" the clause to a noun, though.

