SLICHOT

The Mishna Berura maintains that a person in his 12 month mourning period for a parent, or 30 day mourning period for other relatives, cannot lead services on Rosh HaShana or Yom Kippur, but during Slichot, even on the eve of Rosh HaShana or during the 10 Days of Repentance, it is permissible. The Mishna Berura explains further that on the days when the Tachanun prayer is not said, the mourner may lead the Shacharit service if someone else says the Hallel, but he should not lead the Mussaf prayer. The Chayei Adam adds that the Gra would not have allowed a mourner to lead the Shacharit prayer on Rosh Chodesh, but that in the absence of an alternative, he may do so and even lead the Mussaf prayer as well.