Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

Be supposed to

404h

Be supposed to

refers to what is planned or expected to happen, or to duties and

obligations:

Ben

’s supposed to be here at half past ten.

(it is planned or expected)

They didn’t give me a tax code. As a casual employee I

’m supposed to have a

casual-employee tax code. 

(referring to a duty or an obligation)

In the negative, be supposed to can refer to things which are prohibited or

unadvisable. The negative form is not supposed to:

You

’re not supposed to put the coffee-pot in the dishwasher.

Be supposed to

can also refer to what is generally believed to be true:

Isn’t dark chocolate supposed to be good for you?

OTHER VERBS WITH MODAL USES