Question: My mother is about 65 years old. Since she started her monthly period until she reached menopause, she did not know the ruling on making up for missed days of fasting on which she had her monthly period and so on until she reached menopause. She has not made up her missed days of fasting. The average duration of her monthly period was four days. After she learnt that she must make up for her missed days of fasting approximately two years ago, she started to fast three days every month. Therefore, we ask Allaah (Exalted be He) first and then Your Eminence to give us a detailed answer to this question.
Answer: Your mother must make up for her missed days of fasting in Ramadaan starting from the time she reached puberty. In addition, she must also feed a Miskeen (a needy person) for each day she missed which she delayed from one Ramadaan to another if she is able to do this… read more here.