* Zera Avraham 1:12 writes that there's no such thing as arvut on mitzvot derabbanan since we only entered the convert of responsibility for all Jews on the mitzvot we had at the time of Har Grizim and Avel and not mitzvot derabbanan. Ginat Veradim 1:13 assumed otherwise. The Birkei Yosef 124:3 proves that it applies to derabbanan's as well from Rashi Rosh Hashana 29a who says that avrut should have applied to all brachot hanehenin but it doesn't since one isn't obligated to eat. The Ran and Tashbetz 3:79 agree. Since birchat hanehenin are derabbanan, it is clear that arvut applies to derabbanan's. He repeats this in Chaim Shaal 1:75 and adds that Tosfot Brachot 48a also holds that arvut applies to derabbanan mitzvot.</ref>
# Regarding [[Brachot]] HaMitzvah, even if one has already fulfilled one’s obligation one can still fulfill the obligation of others because of the principle of Aravim Zeh BaZeh, the responsibility for our fellow Jew. <Ref> Mishna Brurah 213:14 </ref>
# For Birchat Hanehenin one may not exempt someone else without eating themselves because it isn't obligatory to eat and so there's no obligation for one Jew to exempt another Jew unless he is also going to eat. Some exceptions include Kiddush Friday night, Kiddush Shabbat day, and Hamotzei of Motzei Matzah.<ref>Rosh Hashana 29b. Rabbi Akiva Eiger Pesachim 106a s.v. hava writes that from Tosfot it is evident that even for the Shabbat day Kiddush it is possible to have yatzah motzei even if the one making the bracha doesn't drink.</ref>
# For a Bracha of Shevach such as Birchot Hashachar, Baruch She'amar, and Yishtabach there is a dispute whether one fulfill someone else's obligation even though one already fulfilled one's obligation. <ref>
* The Ritva (Rosh Hashana 29a s.v. tani) writes just like there is a concept of yatzah motzei for birchot hamitzvah there is also one for birchot hashevach. Hagahot Ashuri (Rosh Hashana 3:13) agrees and applies it to Birchat Hashachar and Baruch She'amar. The Meiri (Rosh Hashana 29a s.v. brachot), however, argues that one may not fulfill the obligation of someone else for birchot hashevach just like for tefillah. He concludes that for Yishtabach if one already fulfill his obligation he can't repeat it for the congregation.