298. Forgetting on Rosh Chodesh, et al.
44:14 If someone neglected to say Yaaleh v’Yavo on Rosh Chodesh, he should recite the text, “Blessed are You, Hashem our G-d, King of the Universe, Who gave new months to His nation Israel, for a remembrance.” Unlike the compensatory prayer for Shabbos and yom tov, there is no concluding phrase to this text. This text would be recited whether one forgot Yaaleh v’Yavo at night or by day. If one forgot Yaaleh v’Yavo on Chol HaMoed, he says the text “Blessed are You, Hashem our G-d, King of the Universe, Who gave holidays to His nation Israel, for happiness and rejoicing, this day of (name of Festival). Blessed are You, Hashem, Who sanctifies Israel and the seasons.” (Mishnah Brurah 188:27 says to omit the concluding phrase.) If one forgot on Rosh Hashana, he says, “Blessed are You, Hashem our G-d, King of the Universe, Who gave Festivals to His nation Israel, this Day of Remembrance. Blessed are You, Hashem, Who sanctifies Israel and the Day of Remembrance.” (There is a difference of opinion regarding the inclusion of a concluding phrase for Rosh Hashana – see Mishna Brurah 188:19. Also see there for the case of a sick person who eats on Yom Kippur and forgets to add Yaaleh v’Yavo.) If one only realized his error after starting the next blessing, he need not start bentching over. This is because there is no obligation to eat bread on Rosh Chodesh, Chol Hamoed or Rosh Hashana.
44:15 If a day is both Shabbos and Rosh Chodesh, and one forgot both R’tzei and Yaaleh v’Yavo, he should say, “Blessed are You, Hashem our G-d, King of the Universe, Who gave Shabbos to His nation Israel for rest, in love, as a sign and a covenant, and the new months for a remembrance. Blessed are You, Hashem, Who sanctifies Shabbos, Israel, and the new months.” Rosh Chodesh does not normally have a concluding phrase but Shabbos does, so this phrase reflects both Shabbos and Rosh Chodesh. If one remembered R’tzei and forgot Yaaleh v’Yavo, realizing his error after starting the fourth bracha, he does not go back. Conversely, if he remembered Yaaleh v’Yavo and fogot R’tzei, he must go back. These rules also apply in the case of Chol Hamoed and Rosh Hashana.