Verbatim · Ayatollah A. Sistani
A woman must perform the Qadha of the fasts which she has missed during her menstrual period. However, Qadha of prayers is not obligatory on her .
Ayatollah A. Sistani sistani.org Q&A #15233 other marjas may differ
This is one of the cleanest divergence points between Shia and Sunni fiqh, and one of the most-Googled questions in the niche.
In Shia Jaʿfari fiqh (per A. Sistani):
- Daily prayers (the five ṣalawāt) missed during hayd → no qadāʾ owed. A. Sistani Ruling 1355 is the general exemption. The five daily prayers do not accumulate as a debt during your period. And you do not make them up after.
- Ramadan fasts missed during hayd → qadāʾ owed. Every fast missed because of hayd has to be made up later. If they cannot be made up before the next Ramadan, fidya is owed in addition to the still-outstanding qadāʾ.
Use the qada fast estimator to ballpark the total. Use the fidya calculator for the make-up arithmetic.