I asked much the same question a few weeks ago. The thread is "Indoor newbe - beddings".

I have not added card stock to my bin and I have pulled off the glossy printed side of corrugated boxes before tossing to the bin.

The answer I was given was stick to the corrugated card board which are the larger and more sturdy boxes. The printed card stock like used in cereal boxes and pop/beer cases can be added. But there is a good recycling stream for this material.

My reservation is you never know what they use in the glossy inks. I'll use the VC in vegetable gardens and that produce will feed my family which includes my pregnant wife and toddler.

I agree with mr_yan on avoiding glossy labels on cardboard boxes. There is a tutorial in the starter section as he mentions written by the person who started Dave's Garden which talks about using cardboard. He first soaks the cardboard in a large tub of water before shredding. If any glossy labels are attached, they should come off. If not, discard that section. Although colored inks commonly used in newsprint are no longer considered toxic to worms, I still avoid using them, as well as glossy prints from newspaper. I am strictly a peat moss man, and I use cardboard only for raised bed liners or mulching. I do have a friend however who swears by cardboard and has had great success with using it. He grows some very sensitive exotic plants and the spent media from cardboard vermiculturing works well for him.