DAI RISPOSTE - English

I am not sure what you mean, but "should" is not a verb but a modal auxiliary used to improve the meaning with an ability, permission or possibility.

If you want to use this as a polite form, it cannot have the meaning of "permission". (e.g. You should do this), as this would be too informal.
It will usually not have the meaning of "possibility" either in formal (polite) texts (e.g. This should work)
It can be used as "capability" though in formal texts (e.g. "The president should be in his office at all times") but you will more likely find a formal "to be" construction (e.g. The president is to be in his office at all times).

So, the modal "should" can be used in formal texts when you are talking about a capability, though there are other more common options too. I hope that's what you asked, otherwise you can send me a message for more info.