Leaving the mosque during I'tikaaf to mark attendance is not considered a valid Shariah excuse or body necessity. Therefore, it is not permissible for a person observing Sunnah I'tikaaf to leave the mosque for this reason.
Additionally, marking attendance and returning to the mosque without performing any work is a form of dishonesty towards one’s employer, which is not permissible under Shariah law.
Therefore, the individual should take a formal 10-day leave from work, make the intention to observe Sunnah I'tikaaf, and remain in the mosque for the full 10 days. If a leave cannot be obtained, the person may spend some time after returning from work in the mosque with the intention of observing Nafl I'tikaaf.
۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔۔
دلائل:
تبيين الحقائق شرح كنز الدقائق: (350/1، ط: دار الكتاب الإسلامي)
(ولا يخرج منه إلا لحاجة شرعية كالجمعة أو طبيعية كالبول والغائط) لما روينا من الأثر عن عائشة - رضي الله عنها - ولما روي عنها أنها قالت «كان النبي - صلى الله عليه وسلم - لا يدخل البيت إلا لحاجة الإنسان إذا كان معتكفا» متفق عليه تريد البول والغائط.
Allah the Almighty knows best.
Darul ifta Al-Ikhlas, Karachi.