It all depends whether you're asking about turn-based ('online chess') or LiveChess.
In turn-based-chess: No, there doesn't seem to be a setting to protect you from inadvertently accepting unrated games. (Even a pop-up: "Are you sure you want to play unrated?" would be useful.)
In LiveChess, YES! Click on SEEK FILTER (at the bottom of the Challenges tab pane). Tick RATED ONLY, and click SAVE.
(Incidentally, there is a small "u" next to unrated games in the TIME column.)
(See also ratings34)
Can someone please tell me how to only play rated games as my settings, though its set to 'Rated Only', keeps giving me 'non-rated' games. This is so annoying especially when u beat a higher rated player - thats alot of points missed that could have me up to a 1300 player instead of a 1100!!
I contacted a member of staff and they advised me to seek the 'DETAILS TAB' of which I can not locate - only 'settings' seems to give me this option. Iam probably just being 'blind' or something but I would appreciate some help people... thanks all and have a good time on here!