Missed Fasts Without a Valid Excuse
According to the majority of jurists, a person who missed fasts without a valid reason or excuse must make up for all the days he missed.
in other words, It will not be acceptable for such a person to feed a needy instead of fasting a day to make up for a fast day missed. This can only be done when one is not able to fast at all. But if one is able to fast, nothing but fasting will be accepted from him or her.