Is Tachanun said by Kerias Shema Sheal Hamitah of Erev Yom Kippur?
Those who do not decrease in the amount of Selichos recited on the night of Erev Yom Kippur are to say Tachanun at night in Kerias Shema Sheal Hamitah. However, those who are accustomed to decrease in the amount of Selichos said on Erev Yom Kippur, are not to say Tachanun at night. Regarding the Chabad custom: Some write one is not to say Tachanun by Kerias Shema Sheal Hamitah, however this matter requires further analysis.
 Based on Admur 604:3
 Hiskashrus footnote 15
 Tzaruch Iyun on the above ruling in Hiskashrus as the Chabad custom is to never say Selichos during Aseres Yimeiy Teshuvah, hence what proof is there that we consider it a Yom Tov from the night as hold some opinions? To note that in the Siddur Admur writes that Kaparos is followed after Selichos, hence showing that Selichos is said at the night of Erev Yom Kippur. However, it is unclear if it is a normal amount of Selichos or a lesser amount.