If a person sees the new moon of Ramadaan but could not tell the superiors or was not believed about seeing it, should he fast alone, and what about Eid? Should he break the fasting alone?.
Some of the scholars are of the view that he should fast by himself, but the correct view is that it is not permissible for him to fast by himself or to break the fast by himself, rather he should fast with the people and break the fast with them, because the Prophet (peace and blessings of Allaah be upon him) said: “The fast is the day when you (plural) fast and the breaking of the fast is the day when you break the fast.” But if he is in the wilderness and has no one with him, then he may start and end the fast on the basis of his own moon sighting. End quote.
Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him)