A year back, I was going through a big problem and I made a minnat saying that if Allah (SWT) resolves my problem I will fast for 40 days , not continuously but whenever I get time. Due to work I am unable to do the fast. I have done 11 fasts till now. I wanted to know whether doing these kinds of minnats is correct or not. And since I am unable to do fasting what could be the kaffarah.
بسم الله الرحمن الرحيم
Due to vow (minnat), the forty days fasts became wajib on you. You should fast for forty fasts one by one until you are capable to do so and when it is beyond your capacity then you can pay the kaffarah of the remaining fasts. The kaffarah of one fast is one 1633 gram of wheat or its price which should be given in charity to the poor.
Allah knows Best!
Darul Uloom Deoband