If a woman starts menstruating after the prayer time has begun but before performing the prayer, does she have to make…

If a woman who is obligated to perform prayers begins menstruating after the prayer time has entered but before she has performed the prayer, according to the Hanafi school, she is not required to make up that prayer. This is because, if she has not performed it earlier, the obligation to perform the prayer is established at the end of the prayer time. In this regard, if a woman goes to bed in a state of purity and realizes upon waking that she has started menstruating, she is considered to have begun menstruating from the moment she woke up and does not perform the prayer for that time. Conversely, if a menstruating woman goes to bed and, after the prayer time has ended, wakes up to find that she has become pure, as a precaution, she is considered to have become pure from the time she went to bed and is required to perform the prayer for that time. (Ibn Abidin, Radd al-Muhtar, 1/291)

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu