Hi .. my mum died last year the day after Yom Kippur 11 Tishri.. she was buried after Shkiah on the 12th of Tishrei . When do I stop saying Kaddish ? Thank you

ב"ה First of all, may Hashem comfort you בתוך שאר אבלי ציון וירושלים The Yahrtzeit is determined by the day of death. However, the 11 months for Kaddish are determined by the date of burial. Therefore, if the burial was on the 12th of Tishrei, then the last day to say Kaddish is the 11th of Elul.( גשר החיים ל:ט: י) All the best and Besorot tovot.