been 18 or over at the time he or she lived with you;
had a net income of less than $16,989 (line 236 of his or her return, or what line 236 would be if he or she filed a return); and
been dependent on you due to physical or mental infirmity or, if he or she is your or your spouse or common-law partner's parent or grandparent, born in 1940 or earlier.
Regarding to Line305, I just called the tax filing agent to double confirm if I can put my baby as a dependent to claim tax credit, I was told that if I didn't have a spouse or seperated with him in 2006, then I can put my baby's credit in... otherwise, the baby will not be considering as a dependent...