Question :
When I was younger, thirteen years old, I fasted Ramadaan and did not fast for four days because of my period. I did not tell anyone about that because I felt too shy. Now eight years have gone by. What should I do?

Answer :
Praise be to Allaah.
You made a mistake by not making up those days all this time. This (i.e. menstruation) is something which Allaah has decreed for the daughters of Adam and there is no shyness in matters of religion. You have to hasten to make up those four days, then in addition to making them up, you have to offer expiation, which is to feed one poor person for each day, by giving two saa� of the usual staple of the country to one or more poor persons.

Fataawa Shaykh Ibn Baaz