Date: 13 Kislev 5592
From: Rabbi Moshe Sofer
To: Unknown recipient
Three questions addressed to Rabbi Akiva Eiger: whether a replacement cantor on Yom Kippur must restart the berachah, why the Kohanim reader begins from Sim Shalom rather than Retzei, and whether Ma'ariv fulfills the Torah obligation of Havdalah. The Chasam Sofer validates the replacement cantor's practice, explains that liturgical insertions break the unity of the final berachos, and argues one implicitly reserves the Torah Havdalah obligation for wine.
Source: Shu"t Chasam Sofer OC §21