We have many narrations that Sahm Imam which is half of the Khums must be given the Marje' of Taqleed being a deputy of the Imam during the occultation of imam Al-Mahdi (AS). You can read many of theses narrations in Wasa'il al-Shia by Al-Hurr Al-A'amily in the chapter of Khums.
'Wassalam.