The World Federation One Stop Fiqh

Ruling 1678

If a person delays keeping the qaḍāʾ fasts of the month of Ramadan for a few years, he must make them up; and for the first year’s delay, he must give one mudd of food to a poor person for each missed fast [as kaffārah]; however, for the delay in the later years, there is no obligation on him.12

12 For example, if someone has to make up one fast and he delays making it up for three years, he must give one kaffārah [i.e. one mudd of food] to a poor person, not three kaffārahs.