Question: Should the voluntary Sawm (Fast) of the six days of Shawwaal be observed directly after Ramadaan, following the day of ‘Eed-ul-Fitr (the Festival of Breaking the Fast), or is it permissible to start observing it several days after ‘Eed-ul-Fitr, during the month of Shawwaal?
Answer: It is not necessary to observe this Sawm directly after ‘Eed-ul-Fitr. It is permissible to start observing it one or more days afterwards. The six days can be observed either consecutively or separately during the month of Shawwaal, whichever is easier. This matter is open to choice, as this Sawm is Sunnah (supererogatory act of worship), not Fareedah (obligatory act)... read more here.