The Tikkun for one who stumbled in the sin of not properly honoring and fearing his parents:

One who transgress the command of honoring and fearing his parents, is to perform the following Tikkunim for his sin:

• He must ask forgiveness from his parents.[1]
• He must resolve from now on to properly honor and fear his parents.[2]
• He is to fast a certain number of fasts or redeem these fasts with charity according to his level of affordability.[3]

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[1] Chida in Shiyurei Bracha 241:3; Sefer Chassidim 573; Nachal Kadmonim Parshas Shemos; Yosef Ometz 87

Other opinions: Some Poskim question whether one is required to ask forgiveness from his parents if he did not properly honor or fear them, as perhaps this command is between man and G-d and hence one must only ask forgiveness from G-d. [Minchas Chinuch Mitzvah 33] However, certainly if one’s parent was offended by the child then according to all opinions the child must ask them for forgiveness as would apply if they offended any other person.

[2] Rambam Hilchos Teshuvah; Shemos Raba 23:3; Zohar 2:217; Yuma 6b

[3] See Shaar Ruach Hakodesh of Rav Chaim Vital Tikkun Ches [fast 26 fasts]; Tikkun Tes [fast 45 fasts, Gematria of Av Eim with Kolel]; Ben Ish Chaiy Shoftim 2:22 [redeem with charity if weak]; Tanya Igeres Hateshuva chapter 3 [today that we are weak redeem with charity]

How much money to give to charity: One should give money to charity in accordance with his affordability. If one can afford it, he should give the value of 13 grams of silver to charity which is the equivalent of 12 Peshutim, per day of fasts. If one can afford to give more, than he should give more, and if one can’t afford to give the above amount then he should give less, each person according to his capability, as the main thing is to feel the pain of the money. [See Admur 334:28; Rama 334:26; Terumas Hadeshen Pesakim 60; M”A 568:33; Az Nidbaru 5:51; Piskeiy Teshuvos 334:10; Pesakim Uteshuvos Y.D. 240:1 footnote 22] One is to give the charity to poor Torah scholars and other charitable institutions.