It was narrated that Abu Ayyub al-Ansari (may Allaah be pleased with him) said that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: "Whoever fasts Ramadaan and then follows it six days of Shawwaal is like fasting for the age." Narrated
by Muslim (Muslim, 2/282)

The launch of the hadeeth indicates that the whole month of Shawwaal is the subject of the fast of these six, whether it is fasted or sporadic, from the first or the last. It is broad and the initiative to do good deeds is always better.

Among the issues related to fasting six Shawwal are:

First: This credit is not given to anyone who has taken the time to spend the missed Ramadaan first. Then he will follow him on the sixth day of Shawwaal.

Whoever fasts on a day of six days, then it seems to him that he breaks his fast, then there is nothing wrong with it because fasting is voluntary, and he fasts in his place for another day.

It is not valid to fast six days of Shawwaal with the intention of the day, so it is not necessary for fasting to make up the intention from the night. For it is a fast to volunteer and the fasting of volunteering is not required for his health. From daytime they do not differentiate between absolute volunteering and volunteerism.