Checking for the End of Menstruation Before Ghusl - Jurisprudential Answers - Book of Purification

Ahmed al-Hasan Response:

She must check if she is uncertain whether she has become free of menstruation. Her husband may have intercourse with her before ghusl if she has checked, while intercourse before ghusl is forbidden if she has not checked. If she performs ghusl without checking, her ghusl is valid and her husband may have intercourse with her. There is no expiation if they later discover that she was still menstruating.