If you do not have a Minyan on Rosh Hashana what should you do regarding Shofar blowing in Musaf and after Musaf?
No Shofar is blown in this case during Musaf.
שוע”ר תקצב ז.
However, after davening, it is proper to blow 70 sounds in order to hear a total of 100. The Shofar blown during Mivtzoim etc. may count for this purpose.
It is important to note that when davening without a Minyan on Rosh Hashana one should make sure to blow the Shofar and daven Musaf only after 3 hours of the day has passed, i.e., only after Sof Zman Kerias Shema.
שם תקצא יג-יד.
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