Can You Fast the Day after `Eid Al-Fitr?
Question

Is it permissible to make up a missed fast on the second or third day of Eid?.
Praise be to Allah.`Eid Al-Fitr lasts for just one day, which is the first day of Shawwal . 
With regard to the commonly-held belief among people that `Eid Al-Fitr lasts for three days, this is merely a custom that is known among the people and has nothing to do with any Shar`i rulings. 
Al-Bukhari (may Allah have mercy on him) said: 
Chapter: Fasting on the day of Al-Fitr. 
Then he narrated (1992) that Abu Sa`id (may Allah be pleased with him) said: The Prophet (peace and blessings of Allah be upon him) forbade fasting on the day of Al-Fitr and An-Nahr. 
Based on this, the day of Al-Fitr is just one day, on which it is prohibited to fast, As for the second and third days of Shawwal , it is not prohibited to fast those days; it is permissible to fast it to make up a missed Ramadan fast or as a voluntary fast . 
And Allah knows best.