Answered by Shaykh Sikander Hashmi
What if someone is making up a fast of Ramadan and then break it deliberately?
In the name of Allah, Most Compassionate, Most Merciful
The fast will be rendered invalid and the sister will have to fast again to make up for the missed Ramadan fast. However, in this case, expiation (kaffara) will not be required.
Expiation is necessary only if a fast is broken in Ramadan. Expiation is not due for the breaking of any fast outside the month of Ramadan, even if the fast that was breached was being observed to make-up for a fast missed in Ramadan. (Talimul Islam; Book IV, Section II, p. 167)
Verily, Allah knows best.
Sikander Ziad Hashmi