It is permissible to do ‘Umrah at any time of the year
Question

                Is it permissible to do ‘umrah at any time of the year? Or is it not permissible to do it except during the months of Hajj?.
Praise be to Allah.
    It is permissible to do ‘umrah on all days of the year, even 
    during the months of Hajj. If a person does it during the months of Hajj and 
    does Hajj after that in the same year, then he is said to be doing tamattu’ 
    for ‘Umrah and Hajj. If he does it with Hajj, then he is doing qiraan and 
    combining Hajj and ‘umrah. Both those who are doing tamattu’ and those who 
    are doing qiraan must offer a hadiy of an animal that is acceptable as an 
    udhiyah, if he is not a resident of Makkah. If the pilgrim does ‘umrah in 
    Dhu’l-Hijjah after the days of al-Tashreeq, it is permissible and he does 
    not have to offer a hadiy. 

    And Allah is the source of strength. May Allaah send 
    blessings and peace upon our Prophet Muhammad and his family and companions. 
    End quote. 

    Shaykh ‘Abd al-‘Azeez ibn ‘Abd-Allaah ibn Baaz, Shaykh ‘Abd al-Razzaaq al-‘Afeefi, Shaykh ‘Abd-Allaah ibn Ghadyaan