Forgot Shehechiyanu during Pesach Kiddush:[1]

One who forgot to recite the blessing of Shehechiyanu during Kiddush, prior to drinking the wine, is to recite it afterwards, immediately upon remembering. Even if he only remembered the next day, he is to recite Shehechiyanu. [It may be recited even without a cup of wine.[2]] It may be recited anywhere upon remembering, even if he is in middle of the marketplace. If in the Diaspora one did not remember to recite Shehechiyanu until the second night of Yom Tov began, then he fulfills his blessing of Shehechiyanu of the first night through the Shehechiyanu recited after Kiddush of the second night.[3] If he forgot to say the blessing of Shehechiyanu during Kiddush of the second night [in the Diaspora] then he is obligated to recite the blessing whenever he remembers throughout the seven days of Pesach.[4] This applies until the end of Achron Shel Pesach [the 8^th day of Pesach].[5] [In Eretz Yisrael, if he did not recite the blessing on the first day of Pesach, he is obligatedo recite it until the end of last day of Pesach, which is the end of Shevi Shel Pesach. Once Pesach concludes, in Eretz Yisrael after seven days and in the Diaspora after eight days, Shehechiyanu can no longer be recited.]

Forgot Shehechiyanu during Sukkos Kiddush:[6]

One who forgot to recite the blessing of Shehechiyanu [during Kiddush, prior to drinking the wine, is to recite it afterwards, immediately upon remembering.[7]] Even if he only remembered the next day, he is to recite Shehechiyanu. It may be recited even without a cup of wine. [Ideally, it may be recited anywhere upon remembering, even if he is in middle of the marketplace[8]] however on Sukkos, when he says Shehechiyanu, he needs to say it inside the Sukkah, in order to exempt also the Sukkah with the blessing, as explained in 641/2.[9] [If in the Diaspora one did not remember to recite Shehechiyanu until the second night of Yom Tov began, then he fulfills his blessing of Shehechiyanu of the first night through the Shehechiyanu recited after Kiddush of the second night.[10]] If he forgot to say the blessing of Shehechiyanu on the first day, and [in the Diaspora] also forgot to say it during Kiddush of the second night then he is obligated to recite the blessing whenever he remembers throughout the seven days of Sukkos.[11] [This applies until the end of Hosahnana Raba. Once Shemini Atzeres begins, Shehechiyanu can no longer be recited.]

Forgot Shehechiyanu-Shavuos Kiddush:[12]

One who forgot to recite the blessing of Shehechiyanu during Kiddush, prior to drinking the wine, is to recite it afterwards, immediately upon remembering. Even if he only remembered the next day, he is to recite Shehechiyanu. It may be recited even without a cup of wine. It may be recited anywhere upon remembering, even if he is in middle of the marketplace. In the Diaspora, this law applies to both days of Yom Tov. [If in the Diaspora one did not remember to recite Shehechiyanu until the second night of Yom Tov began, then he fulfills his blessing of Shehechiyanu of the first day through the Shehechiyanu recited in Kiddush of the second day.[13] Once the Yom Tov of Shavuos concludes, in Eretz Yisrael after one day and in the Diaspora after two days, Shehechiyanu can no longer be recited.[14]]

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[1] Admur 473/2; See also 643/5 regarding Sukkos; M”A 473/1; Eiruvin 40b; Sukkah 47b

[2] Admur 643/5

[3] Admur ibid; Chok Yaakov 473/1

[4] Admur ibid; Eiruvin ibid; M”A 473/1; M”B 473/1

The reason: As the blessing of Shehechiyanu has Tashlumin for all seven days of the festival. [Admur 643/5]

[5] Admur ibid; Suggestion in P”M 473 A”A 1 [although concludes with tzaruch Iyun]’; M”B ibid; Kaf hachaim 473/10

[6] Admur 643/5; See also 473/2 regarding Pesach; M”A 473/1 and 643/1; Eiruvin 40b; Sukkah 47b

[7] Admur 473/2 regarding Pesach

[8] Admur 473/2 regarding Pesach

[9] Admur 643/5

[10] Admur 473/2 regarding Pesach; Chok Yaakov 473/1

[11] Admur 643/5; Admur 473/2 regarding Pesach; Eiruvin ibid; M”A 473/1; M”B 473/1

The reason: As the blessing of Shehechiyanu has Tahslumin for all seven days of the festival, as explained in 473/2 regaridng Pesach. [Admur ibid]

[12] Admur 473/2 regarding Pesach and 643/5 regarding Sukkos; M”A 473/1; Eiruvin 40b; Sukkah 47b

[13] See Admur 473/2 “He is exempt with the Shehechiyanu that he recites over Kiddush of the second night.” This implies that he fulfils his obligation of Shehechiyanu of the first night. Now, although in 473/2 the case erefers to Pesach, in which oine hjas seven days of Tashlumin. Nevertheless, Admur rules that the second day of Yom Tov is part of the tashlumin, and the same would apply here regarding Shavuos.

[14] Elya Raba 494/4; P”M 473 A”A 1 “Safek Brachos Lehakel”; M”B 473/1 and in Shaar Hatziyon 473/5 that intent of M”A 473/1 is that one can say the blessing until the end of Shavuos; Kaf Hachaim 473/11; See Admur 473/2 regarding Pesach and 643/5 regaridng Sukkos that one can make up the Shehechiyanu throughout the seven days of Pesach/Sukkos. However, Shavuos does not contain Chol Hamoed as does Pesach and Sukkos, and hence the above law would not extend to Shavuos.

Other opinions: Some Poskim rule that one who forgot to recite Shehechiyanu on Shavuos may make it up [i.e. Tashlumin] for the next for a full seven days from the start of Shavuos. [Implication of M”A 473/1 “And the same applies every Yom Tov”; Chok Yaakov 473/1, Beir Heiytiv 473/1; P”M 473 A”A 1 that so is implied from M”A ibid]