What is the fidya for fasting? What is fidya in islam?
The fidya is the financial compensation that people must give for every fardh they have not carried out during Ramadhan. These people are; people who do not have the strength to fast or people who have not fasted, without excuse, their qaza fasts until the time of the next Ramadhan. The giving of fidya for fasting has been established with this ayah: “…And upon those who are able [to fast, but with hardship]– they must give a ransom [as substitute]of feeding a poor person [each day]..” One fidya, is the mud amount (687 grams) of food given to the poor person for the one day fast the person could not carry out.
For the person whose Ramadhan fast has been left to qaza, they must make up for this fast until the time of the next Ramadhan. However if they do not make up for this until next Ramadhan and they have no excuse, along with their fast being left to the qaza, they must also give a fidya. Other than this in the case of the woman who is unable to fast because she is pregnant or breastfeeding, there are two different views within the mazhab on the matter of whether she will need to give the fidya along with fasting for the qaza fast.
The elderly person who is unable to fast is not obliged to give the fidya but it is mustahab if they do so.
 Surat Baqarah, Ayah 184