Q: If you start your period (menses) 40 minutes before iftaar time, after you have prayed Asr, is your fast still counted? Also if you don't check but you know you have started bleeding and you check after Iftar and this confirms what you perceived would you still have to keep Qadha? I remember somebody telling me if you start after Asr your fast is valid.
Merely ‘feeling’ or ‘knowing’ that blood has flowed is not regarded as the start of menses. However, when she does a check afterwards and discovers that indeed blood has flowed out onto the underwear, or has soiled the pad, if any, then it will be said that her Haidh had commenced from the time she felt the initial flow. In that case, the fast has also been nullified and Qadhaa has to be kept after Ramadhaan. If upon checking the woman discovers that blood had not flowed out onto underwear or outer pad, then she can consider the fast intact for her Haidh had not yet commenced. And Allah knows best
Mufti Siraj Desai