Fatwa ID: 04604
Answered by: Alimah Nasima Umm Hamza
1) If you take a vow not to do a certain sin if you do it, is a kaffarah needed?
2} If you paid kaffarah for this when you didn't have to, will I need to pay a kaffarah for another broken vow or does the unnecessary one cover it?
3) If I can't remember what kaffarah I paid for (between an obligatory kaffarah, and an unnecessary kaffarah}, should I pay the obligatory one again to be safe?
I am just trying to make amends, so please facilitate me in doing so. Baarakallaahu feekum.
In the name of Allah, the Most Gracious, the Most Merciful
1) Yes kaffarah is required. 
2) Yes you will have to pay for the kaffarah after it has occurred. 
3) You must try to remember what occurred and establish the facts.
Firstly, did you make a vow to stay away from sin?
Then, you break your vow to not commit a sin or not?
If you did and then didn’t pay kaffarah then it is still due.
And if you didn’t break it then no kaffarah is due.
If you did not make a vow then no kaffarah was due in any case.
Allah (SWT) alone knows best.
Answered By Alimah Nasima Umm Hamza
Checked By Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Al-Hidayah, Book X, Chapter 85 Kaffarah, p926, Imran Nyazee Edition
 Al-Hidayah, Book X, Chapter 85 Kaffarah, p924, Imran Nyazee Edition