Islam permits fasting on behalf of a deceased person if they had an excuse, such as illness or travel, and were able but failed to make it up. However, if they were continuously unable to fast, no action is required. Heirs may fast collectively or pay Fidya (feeding the poor) as an alternative.

It is permissible for you to make up missed Ramadan fasts on the day of doubt and one or two days before Ramadan. For more, please see the detailed answer.

If you start an obligatory fast, such as making up a missed Ramadan fast or offering expiation for breaking a vow, it is not permissible for you to break the fast without a valid excuse, such as sickness or travel.