I am saying Kaddish for someone who passed away on ח׳ בְּנִיסָן תשפ״ג, and was buried the next day. On what date and which T’filla do I stop saying Kaddish? This is not for a Karov. It is for someone from the community for whom I am saying Kaddish.
kaddish is said for 11 months from the day of the burial, therefore it is for 11 months from 9th of Nissan, and it is finished the mincha before the 12th month from the burial starts. in your situation, you would say kaddish until and including mincha on the 8th of Adar Rishon.