Indira Ekadasi is observed during the waning phase of moon in the month of September/October. The Indira Ekadasi Vrat Katha is mentioned in the Brahmavaivarta Purana. The story of this Ekadashi fasting was narrated to Yudhishtira by Lord Krishna. This Ekadasi falls during the Pitru Paksha Shradh period and therefore observing it is considered apt for redemption of sins of one’s own and that of forefathers.
Once there lived a powerful, honest and popular king named Indrasena. He was an ardent devotee of Lord Vishnu. Once Sage Narada visited King Indrasena and mentioned about his visit to the abode of Lord Yama, the Hindu God of death.
At the abode of Lord Yama, Sage Narada found the father of King Indrasena. He had not got moksha and was living in the house of Yamraj. The father of Indrasena asked Sage Narada to ask his son to observe Indira Ekadasi so that he will escape from the house of Yama and attain Moksha and reach the feet of Lord Vishnu.
Indrasena immediately agreed to observe Indira Ekadasi for his father and asked Sage Narada to guide him in observing the Ekadasi fasting. Sage Narada explained to the King on how to observe Indira Ekadasi.
The day before Ekadasi one should perform Shradh rites and rituals for dead ancestors and parents. On the day one should only take a single meal.
On the Ekadasi day it is a complete fast. At noon, one should pray for the wellbeing of the ancestors and for their souls to rest in peace. Devotees do not sleep during the night and stay awake by chanting prayers or listening to stories of Lord Vishnu.
The next day after morning prayers, the fast is broken by eating with family members.
As a result of observing Indira Ekadasi, father of King Indrasena got Moksha and reached the abode of Lord Vishnu.