Most Chassidic Groups:1
- On the yahrtzeit of a rabbi with connection to the group (either a previous rebbe, or someone with substantial influence on the group or that town's inhabitants).
- When their rebbe does, e.g. when his child gets married or is circumcised.
- On days when special joyous events happened to their past rebbes, e.g. they were freed from prison or concentration camp, or a decree affecting them was abolished.
- Do say tachanun on on Yom HaAtzma'ut, even if there would be reasons not to say. a) 4
- If there is a circumcision anywhere in that town (common custom is only that synagogue).
- By Mincha.b)
- On Erev Rosh Chodesh if it is after the molad.
- Reb Mendel's chassidim by Mincha, even though it is always before sunset.c)
- From Rosh Chodesh Adar I until seven days after Shavuos.
- Whenever there can be found a reason (e.g. Mincha, Yahrtzeit,...).
a) The current Belzer rebbe himself steps out of his own synagogue to say tachanun alone, if his synagogue omits it by a bris milah. This is even though he is the sandak and mohel and normally would not say tachanun, even in a minyan other that where the bris takes place.2
b) Lev Tahor says tachanun by Mincha, even though they use the Munkatcher siddur.1
c) Reb Mendel keeps the custom of his father, Reb Moshele, who abolished tachanun by Mincha. However, traditionally it is said, and so do Reb Mottele's chassidim, and Reb Yisroel is reinstating the old custom for his chassidim.7
1 Personal experience
2 Heard from Lipa Klein, Montreal, a prominent Belzer chassid who was there
3 Such chassidim
4 Siddur Yetev Lev
5 Siddur Tz'vi Tiferes
6 Viznitzer siddur
7 Montreal's Yisroel-Viznitzer dayan
8 Montreal's Shotzer rebbe's son (See Wikipedia for information about the split within Viznitz)