Birchas Kohanim on Simchas Torah

Rema (O.C. 128,44) “The custom in these countries is that kohanim do not "lift their hands" other than on Yom Tov since it is then that they experience the simchah of Yom Tov and "a good heart blesses" as opposed to other days, even Shabbos, when they are burdened with thoughts about their sustenance and missing work. Even on Yom Tov they only "lift their hands" in mussaf when they are about to leave the Bais HaKnesses in order to celebrate the joys of Yom Tov.” Thus, most Askenazi communities follow this concept of Birchas Kohanim at Mussaf on Yom Tov (including Rosh haShana and Yom Kippur but not including Rosh Chodesh).

However, on the day of Simchas Torah, due to the concern of drinking intoxicated beverages, four major customs developed for this day.

Some Do Not Do Birchas Kohanim at All on Simchas Torah

The Levush, Lekutei Maharik, and the Aruch haShukchan all mention this custom. Also, this was of the custom of the Bais HaKnesses HaGadol in Berlin. Some mention the reason that upon hearing the blessing of Moshe (in the Torah reading of VaZos haBeracha) this would infringe on the honor of Moshe to act as if we needed a further set of blessings.

Some Do Birchas Kohanim During Shacharis and Again in Mussaf

Minhag Frankfurt was that the Kohanim would bless in Shacharis, and not participate in eating and drinking and then bless again in Mussaf. Any Kohanim that did drink would leave the synagogue during the repetition of Mussaf. Some other communities had this custom.

Some do Birchas Kohanim Only in Mussaf

Machzor Vitry writes, "and the Sefer Torah is returned to its place and the people stand for Mussaf...and the Kohanim bless the people." Also, the Eliya Rabbah mentions this custom. So writes the Shulchan haTahor. Further, he discourages the custom to do Birchas haKohanim in Shacharis since this provides tacit approval to those who drink too much.

Some do Birchas Kohanim Only in Shacharis

Pri Megadim cites this custom since people drink due to happiness and have a tendency to throw fruit and candy to the children in the synagogue (which is not pleasant to the Kohanim who would walk without shoes). Many poskim state this custom, including Chasam Sofer, Kitzer Shulchan Aruch, and most communities.