When to Recite Av Harachamim in the Synagogue

There are always disputes in the synagogue about when to recite Av Harachamim. Can we clarify?

Shalom and blessings! The rule is that in any case where Tachanun would not be recited if the date fell on a weekday, Av Harachamim is not recited. This includes when there is a brit milah or a groom on the Shabbat of the Sheva Brachot in that synagogue. Additionally, on any Shabbat when the new month is blessed, Av Harachamim is not recited. However, there is one exception, which is during the days of the Counting of the Omer, because Av Harachamim was instituted in memory of the Crusades that occurred during the Counting of the Omer. It was established that during the Counting of the Omer, Av Harachamim is recited even if it is the month of Nisan, in which Tachanun is not recited, and even if the month of Iyar is blessed, and even if there is a brit milah or a groom in the synagogue, although there are three reasons in one Shabbat, it is recited. However, on Shabbat Rosh Chodesh Iyar, even during the days of the Counting of the Omer, Av Harachamim is not recited. Another exception is Tisha B'Av that falls on Shabbat; although Tachanun is not recited on Tisha B'Av, Av Harachamim is recited.

Shulchan Aruch (Orach Chaim, Siman 284, סעיף 7) Mishnah Berurah (סק 16; 17; 18).