Answered by Ustadh Tabraze Azam
Question: As salam aleykum,
Should a woman fast during her menstruation?
Is an expiation required for missed fasts due to menstruation?
Answer: Wa alaikum assalam wa rahmatullah,
The expiation (kaffara) applies in the case of a major violation due to the sanctity of the month of Ramadan, namely, by eating, drinking or engaging in intimate relations during the fasting hours.
As for during menstruation, it is not permissible nor valid to fast, and the lady need only make up the missed fasts after Ramadan. No expiation is due in such a case.
And Allah Most High alone knows best.
Checked & Approved by Shaykh Faraz Rabbani