Blessing Of Ramzan: Rules of Nafl Fasting and Qaḍā in Islam

It is not permissible to break a Nafl fast without a valid exemption. If a guest feels resentment due to the host not eating with him or if a host feels resentment due to the guest not eating, it is a valid exemption for breaking a Nafl fast to eat with the other, provided that he is certain to make its Qaḍā another day, and that he breaks it before Ḍahwā Kubrā, not after it. (سُبْحَانَ اللّٰه عَزَّوَجَلَّ! This shows how profusely Sharīʻah values the honour of a Muslim). (Fatāwā 'Ālamgīrī, pp. 208, vol. 1)

27. A guest can only break his fast before Ḍahwā Kubrā if the host is not pleased with his mere presence and will resent if the guest doesn't eat, provided he (the guest) is sure to make up for the fast later. However, if the host is pleased with the mere presence of the guest and will not mind if he doesn't eat then the (the guest) will not be allowed to break his fast. (Fatāwā 'Ālamgīrī, pp. 208, vol. 1)
28. It is permissible to break a Nafl fast even after Ḍahwā Kubrā in case of parents' displeasure. One can break this fast any time before 'Aṣr but not after 'Aṣr. (Durr-e-Mukhtār Rad-dul-Muḥtār, pp. 414, vol. 3)
29. A woman should not have a Nafl, vow or sworn fast without her husband's permission. If she does, her husband can make her break it, and if she breaks the fast it will become Wājib for her to make up for it, but she needs her husband's permission even for keeping this Qaḍā fast. However, she can fast of her own accord, if her husband has died or given her a 'Bāin' divorce (a divorce in which becomes invalid and the husband cannot revert).

If the woman's fasting does not cause her husband any problem, she can keep a Qaḍā fast even without his permission. For instance, if he is on a journey or ill or in a state of Iḥrām (pilgrimage) she can keep Qaḍā fasts even if he asks her not to. However, she cannot keep a Nafl fast without her husband's permission even in these cases. (Rad-dul-Muḥtār, pp. 415, vol. 3)

30. She does not need her husband's permission to keep Ramadan fasts or fasts for Qaḍā of Ramadan. She must fast even if he prevents her from fasting. (Durr-e-Mukhtār Rad-dul-Muḥtār, pp. 415, vol. 3)
31. 
    If one is an employee or does a job on wages, he cannot have a Nafl fast without his employer's permission because fasting will cause sluggishness at work. However, if he is strong enough to work normally and completely without sluggishness despite fasting, he does not need permission to keep a Nafl fast in this case. (Rad-dul-Muḥtār, pp. 416, vol. 3)

32. For Nafl fasts, a daughter does not need her father's, a mother does not need her son's, and a sister does not need her brother's permission. (Rad-dul-Muḥtār, pp. 416, vol. 3)
33. If parents prevent their son from having a Nafl fast for fear of illness, he must obey his parents. (Rad-dul-Muḥtār, pp. 416, vol. 3)

Here are twelve points about the acts that make only Qaḍā necessary. Doing Qaḍā means observing one fast after Ramadan for each missed fast.

Twelve points about Qaḍā

1. If somebody ate, drank or engaged in intercourse assuming that some part of night was still left but he came to know later on that it was the time of dawn (Ṣubḥ-e-Ṣādiq), so his fast would be invalid. It is necessary to keep this fast as Qaḍā later on. (Rad-dul-Muḥtār, pp. 380, vol. 3)
2. If somebody is forced to the extent of Ikrāh-e-Sharʻī to eat, as it is a valid exemption for eating, only making up for that fast will be mandatory for him, even if he eats with his own hands. (Durr-e-Mukhtār, pp. 402, vol. 3)

The summary of this ruling is that if somebody forces the fasting person to break his fast by threatening him to kill, cut any body part or beat severely, and the fasting person knows that the threatening person would do what he threatens, so Ikrāh-e-Sharʻī is there, the fasting person can break his fast in this situation, but it is mandatory to make up for it later.

3. If somebody ate, drank or engaged in intercourse in the state of forgetfulness, or ejaculated due to a lustful look, or experienced a nocturnal emission, or vomited and thus assumed that his fast had broken and so he ate something deliberately, only making up for this fast would be necessary for him. (Durr-e-Mukhtār, pp. 375, vol. 3)
4. Inhaling medicine through the nose in the state of fast will invalidate the fast and it would be mandatory to make up for it. (Durr-e-Mukhtār, pp. 376, vol. 3)
5. Eating a stone, grit, soil, wool, grass, paper or anything else that people feel disgusted by, will invalidate the fast but one will only have to make up for it (expiation is not Wājib). (Durr-e-Mukhtār, pp. 377, vol. 3)
6. If rainwater or flake of snow goes down the throat, the fast will become invalid and it would be mandatory to make up for it. (Durr-e-Mukhtār, pp. 378, vol. 3)
7. Likewise, swallowing a large amount of sweat or tears will invalidate the fast. One will have to make up for it. (ibid)
8. If somebody continued to eat assuming that some part of night was still left but he came to know later on that the time of Saharī had ended while he was eating, his fast would be invalid and he will have to make up for it. (Rad-dul-Muḥtār, pp. 380, vol. 3)
9. If somebody breaks the fast assuming that the sun had set, but came to know later that it hadn't set, his fast will become invalid and he will have to make up for it. (Rad-dul-Muḥtār, pp. 380, vol. 3)
10. If someone mistakenly does Ifṭār before the sunset as a result of premature utterance of Maghrib Aẓān or siren-wailing and comes to know later on that siren or Aẓān started earlier than the sunset, even if it is not his fault his fast will still be invalid and he will have to make up for it. (Derived from Rad-dul-Muḥtār, pp. 383, vol. 3)
11. Unfortunately, people have been heedless about the matters of Sharī'ah these days. Every Muslim should be careful about his fasts himself. Rather than relying on sirens or radio and TV announcements or even the Aẓān, everyone should get the correct information of Saharī and Ifṭār timings.
    
12. During Wuḍū, if water reached the brain or went down the throat while sniffing water into nose the fast would become invalid and its Qaḍā would be mandatory provided one was aware that he was fasting. However, if one was unaware of the fast at that moment his fast will not become invalid. (Fatāwā 'Ālamgīrī, pp. 202, vol. 1)