Reference: Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-‘Ilmiyyah wal-Iftaa. – Fatwa No.6355
Fataawa Ramadhaan – Volume 1, Page 378, Fatwa No.337
Question: What is the ruling regarding a 15 year old not fasting during Ramadhaan, with the excuse that he is extremely tired and he does not have the ability to complete his fast on a particular day. And if he were to make up the fast [which he missed], is it then permissible for him to do so after the following Ramadhaan has passed?
Response: It is haraam for a responsible Muslim who is aware of all his faculties; has attained puberty, is currently locally-based [as opposed to travelling] and is in good health not to fast during the day in Ramadhaan. And if the fasting becomes difficult for him and he is compelled to break his fast, just as a person would feel compelled to eat dead meat [if he was hungry and no other food was available, such as if he was in the desert, etc.], then it is permissible for him to eat a sufficient amount as to allay his hunger. He should then continue to refrain from all that breaks the fast for the rest of the day, then make up the fast for this day after Ramadhaan has passed. If he delayed making up this fast until the [arrival of the] following Ramadhaan, then he is required to make up the fast [which he missed] in addition to feeding a poor and needy person for each day he missed.
[Note,] whoever is 15 years old, then he has attained puberty; and likewise [is the case], if he excreted semen by way of desire by having had a wet dream or by other than this, or if he notices pubic hairs around his private part; in addition to starting the menses with respect to the girl.
And with Allaah lies all success, and may Allaah send prayers and salutations upon our Prophet Muhammad (sal-Allaahu ‘alayhi wa sallam) and his family and his companions.