I came to experience my menses in Ramadan. However, my menses did not come during the fasting time; rather it would come after the ‘Isha’. This would happen every day; the blood would flow after the ‘Isha’ time and stop before the Fajr time. That is, my menses would never come out during the fasting time. Rather, it would start after the ‘Isha’ time at 9:00 pm. The question is: Is my fasting valid? Shall I make up for those days?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

According to the predominant opinion of Muslim scholars, the purity that takes place during the menstrual period is a valid state of purity with which the woman needs to perform ghusl (ritual bath) and observe acts of worship, including prayer and fasting. In Mataalib Uli An-Nuha, it is stated:

The minimum length of time to prove the purity of a woman from menses if it takes place throughout the menstruation period is that the woman becomes completely pure to the extent that if a cotton swab is inserted in the vagina it would not carry a blood stain. It does not matter how long or short such a state of purification lasts. Having sexual intercourse with the woman is permissible; meaning with the woman whose menstrual bleeding stops during her period provided that she performs ghusl in the interval during which she becomes pure from its menses. This is because Allah describes menses as being harm. So if menses stops, harm should go away.  

That being said, if you recognize purity from menses and the blood stops flowing so that no traces exist in the vagina and if you insert a cotton swab in the vagina it will not carry any stains, if this is the case and you perform ghusl and pray, then your prayer should be valid. Also, if you fast and the blood does not flow again during the fasting time, then your fasting should be valid. If you see menses again during the fasting time even if for a moment before the sunset, then you have to make up for the day later.   

Allah knows best.