Q. A Chassan (groom) that is getting married on Rosh Chodesh and therefore he is not fasting, does he say Viduy (confession) when he davens Mincha?
A. Poskim disagree. Kerem Shlomo (E.H. 65 14), Pischei Tesuva (E.H. 61: 9), Siddur Iyun Tefila, Yad Yitzchok (2: 103), Levushei Mordechai (E.H. 49) and others maintain that the Chassan and Kallah recite Viduy even during Rosh Chodesh.
However, Yalkut Hagershuni (2: 11), Toras Yekusiel (141: 42), Shulchan Hoezer (p. 128), See also Nitei Gavriel (Nissuin 1 p. 78) and others maintain it should not be said.
Horav Shlomo Miller’s Shlit’a opinion is that traditions vary and one should keep his own.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a