House of Mourning – Tachanun is not recited in a house of mourning because we do not want to arouse the Midas Hadin which envelopes a mourner.153 If a mourner comes to shul during shivah154 and serves as the chazzan, the congregation omits Tachanun.155 If he does not serve as chazzan, he omits Tachanun, but the congregation recites it.156
Presence of a Groom – A groom does not recite Tachanun on the day of his wedding or on the seven days of Sheva Berachos.157 When he is present in a minyan during Sheva Berachos 158 the entire congregation omits Tachanun.159 Some Poskim rule that even if the groom does not join the minyan but is present while the minyan is active, he exempts them from reciting Tachanun.160 Conversely, some Poskim rule that if the groom was part of the minyan, but left before the time for Tachanun, they are required to recite it.161
If the wedding will take place before nightfall, there are various customs whether Tachanun is omitted at Shacharis and Minchah, recited at Shacharis and omitted at Minchah, or recited at both.162
If the wedding will take place after nightfall most authorities agree that Tachanun is not omitted on the day of the wedding.163 However, if Minchah is davened by the members of the wedding party in the wedding hall right before the actual wedding is to take place, then Tachanun is omitted by all who are assembled.164
Bris Milah – Tachanun is not recited at either Shacharis or Minchah if a Bris Milah will be taking place at that minyan.165 In addition, those who are the primary participants of a bris milah – i.e., the father of the child,166 the mohel and the sandak – do not recite Tachanun for the entire day of the bris.167 If they are present in a minyan of Shacharis,168 even if the bris will not be taking place in that shul they exempt the congregation from reciting Tachanun.169 There is no reason for any of the primary participants of a bris milah not to go to shul,170 and even a professional mohel [or a Torah leader who serves as a sandak daily] who davens in a set minyan every day exempts the congregation on all days on which he performs a bris milah [or serves as a sandak], and need not alternate his place of davening.171 A minyan which is davening in a shul in which a bris had taken place earlier that day should recite Tachanun.172
When Tachanun is omitted due to a bris milah, or the presence of a groom, it is not necessary for members of the congregation to recite Tachanun later.173 Similarly, non-mourners who daven at the house of a mourner do not need to recite Tachanun even after leaving the house of mourning.174
On a fast day, if a Bris Milah is to be held in the minyan, or if a groom is present, although Tachanun is omitted, Selichos175 and Avinu Malkeinu176 are recited.177 However, these prayers are not recited by primary participants in the bris milah and the groom themselves.178 During the days of Selichos, a groom and the primary participants of a bris milah must recite Selichos.179 There are differing opinions about the recital of Tachanun at the end of Selichos.180
Some Poskim rule that if one is davening Shacharis or Minchah in a hall in which a bar mitzvah or pidyon haben celebration is to take place immediately after davening, Tachanun is not recited.181
If Tachanun was mistakenly omitted on a day on which Kerias HaTorah is performed, and the Sefer Torah has already been removed from the ark, the congregation should commence with Kerias HaTorah and recite Tachanun afterwards.182
153 Shulchan Aruch 131:4 with Mishnah Berurah, note 20. This is true even if the mourners are not present (Kitzur Shulchan Aruch 22:5; Kaf Hachaim 131:66). Even if there are no mourners at all, some have the custom to omit Tachanun at the house of the deceased during the seven days following death; see Mishnah Berurah ibid.; Gesher Hachaim I, 20:3-1.
154 This is still applicable at Minchah on the seventh day of shivah. Although the restrictions of shivah are lifted after Shacharis, the status of a mourner during shivah regarding Tachanun is retained until the end of the seventh day (see Kitzur Shulchan Aruch 22:5; Da’as Torah 131:4).
155 Gesher Hachaim I, 20, 3:11; R’ Shlomo Zalman Auerbach, cited in Nachamu Ami 18:18. See, however, Shearim Metzuyanim Behalachah 214:2, who recommends that a mourner not serve as chazzan in shul during shivah because it will cause the congregation to miss Birkas Kohanim and Tachanun.
156 Entire paragraph based on Mishnah Berurah 131, note 20.
157 This extends even to the eighth day, if it is still within seven days’ time of the chuppah (Mishnah Berurah 131, note 26).
158 Mishnah Berurah recommends that a groom not join a minyan so as not to exempt them from reciting Tachanun. Nowadays, however, the widespread custom is that we do not dissuade a groom from joining a minyan (Kaf Hachaim 131:87; Lehoros Nassan VIII:96; Teshuvos Vehanhagos III:55; Chazon Ish, cited in Orchos Rabbeinu, I, p. 131 [5774 ed.]; Halichos Shlomo 11, Devar Halachah 10.
159 Shulchan Aruch 131:4. The presence of a bride does not exempt the congregation from reciting Tachanun (Shevet Halevi V:12). However, if the minyan takes place in the home of the bride, Tachanun is not recited (ibid., VIII, 24:2).
160 Da’as Torah 131:4; see Halichos Shlomo, Tefillah 11:7.
161 Terumas Hadeshen, Pesakim 80; Eishel Avraham (Buczacz) 131:4.
162 Mishnah Berurah (131, note 21) cites two opinions, either that Tachanun is recited at both Shacharis and Minchah or is not recited at all. Aruch Hashulchan 131:16 rules in accordance with the lenient opinion. However, Orchos Rabbeinu (ibid.) reports that the Chazon Ish was stringent about this. A minority opinion maintains that Tachanun is omitted only at Minchah; see Yabia Omer III:11 and 12 and Shevet Halevi VII:18.
163 Halichos Shlomo 11, Devar Halachah 11; Ashrei Ha’ish, Orach Chaim I, 24:7.
164 Ashrei Ha’ish ibid., 8; Shevet Halevi VII:18.
165 Shulchan Aruch 131:4 with Birkei Yosef cited in Sha’arei Teshuvah 12. See also Ashrei Haish I, 24:9. [Some Poskim (R’ C. Kanievsky cited in Ishei Yisrael, p. 769; Tzitz Yisrael VII:9) rule that if a bris milah will be held at Minchah, Tachanun is already not recited at Shacharis in that shul.]
166 Some Poskim rule that this is only if the father of the child will actually be present at the bris (Amudei Hashulchan 104, citing R’ Shlomo Hakohen of Vilna). Others do not make this distinction (Eishel Avraham [Buczacz] 131). Yabia Omer (III:12) rules that a father who will not be present at a bris does not recite Tachanun but does not exempt a congregation from reciting Tachanun.
167 Mishnah Berurah 131, note 22. If possible, they should not serve as chazzan for Minchah (Minchas Yitzchak VIII:29).
168 Or Minchah, if the bris will be taking place after Minchah (see Halichos Shlomo, Tefillah 11, footnote 23).
169 Mishnah Berurah 130, note 22.
170 Halichos Shlomo ibid., 6.
171 Toras Chaim (Sonnenfeld), Nefilas Apayim 3; Emes LeYa’akov 131, footnote 168; Ashrei Ha’ish, Orach Chaim I, 24:2. [A bris milah of a convert does not exempt any of the primary participants from reciting Tachanun (Halichos Shlomo ibid., 8); or the congregation from reciting Tachanun before the bris (Ishei Yisrael 25, footnote 92, citing R’ Shlomo Zalman Auerbach).]
172 Ashrei Ha’ish, Orach Chaim I, 24:9; Halichos Shlomo 11, footnote 8; Shevet Halevi VIII, 24:3. A minority opinion dissents; see Devar Moshe 3.
173 Mishnah Berurah 131, note 21.
174 Mishnah Berurah ibid., note 20. Some Poskim recommend that on Monday and Thursday one recite the passage of Vehu Rachum when he leaves the house of mourning; however, the custom is that one does not recite any part of Tachanun (Chayei Adam 32:33; Kitzur Shulchan Aruch 26:5).
175 Including Vidui (Ishei Yisrael 25, footnote 104).
176 Aruch Hashulchan 131:17; R’ Yosef Shalom Elyashiv, cited in Ishei Yisrael, ibid.
177 Shulchan Aruch 131:5 with Mishnah Berurah, note 28.
178 Sha’arei Teshuvah 131:15; Ketzos Hashulchan, Baddei Hashulchan 24:28.
179 Zeh Hashulchan 131.
180 See Ketzeh Hamateh 602:22; Halichos Shlomo, Moadim II, 1:5; Shevet Halevi IV:54.
181 Halichos Shlomo, Tefillah, 11:9; see also Ishei Yisrael 25:26. See, however, Minchas Yitzchak VIII:11 and Sefer Nekiyus Vechavod Batefillah, p. 242, citing R’ Chaim Kanievsky. There are varying customs regarding the bar mitzvah boy and his father omitting Tachanun on the day the boy becomes bar mitzvah; for discussion see Piskei Teshuvah 131, footnote 141.
182 Halichos Shlomo, Tefillah ibid., 2.