Is there Qadhaa for Sunnah I'tikaaf?

Q: It'kaaf-1:The I'tikaaf during the last ten days of Ramadhaan is sunnah Mu'akkadah alal Kifaayah. will it be necessary to repeat it if it is prematurely terminated because of any reason or through forgetfulness?

Answer: In the stated case, the day's I'tikaaf together with the fast need to be observed. How ever, in the interests of caution and to avoid the difference of opinion in the matter, it is best to observe all ten days I'tikaaf together with the fasts. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.3