Q. Should one change clothing for saying selichos Motzei Shabbos or stay with the Shabbos clothing?

A. Nitei Gavriel (Rosh Hashana 8: 6) writes that those who accustom to say selichos on Motzei Shabbos, the minhag is to recite them wearing Shabbos clothing. He mentions that the reason is that usually we don’t remove Shabbos clothing after Shabbos. However, the minhag Chabad and Stolin is to wear weekday’s clothing.
On question 1764 in regards to A person who can afford only one suit (jacket) and he would like to wear it both on Shabbos as well as when he davens during the weekdays, we wrote “Shulchan Aruch (O.H. 262: 3) rules that one should wear better and specially dedicated clothing for the honor of Shabbos. Poskim disagree as to when is the correct time after Shabbo’s end, to remove those special garments. Mishna Berura (ibid. 8) maintains that one should use them until havdala. The Arizal’s opinion is that they should be worn until after melave malka, since the Neshama Yiseira of Shabbos remains for that time (Kaf Hachaim ibid. 28, Yisod Veshoresh Hoavodo – Shemini).
Yalkut Yosher (p. 58) and others (See Piskei Teshuvos ibid.), assert that the common minhag is to wear them until one goes to sleep. Similarly, they permit wearing Shabbos clothing when attending weddings and simchos, although some are stringent (ibid. quoting Medresh Ruth, Avnei Yoshfo 5: 46)).
In regards to wearing Shabbos clothing for daveninig during weekdays when in need, Horav Shlomo Miller’s Shlit’a opinion is that it can be used for davening.
See also question 1765 regarding one traveling, if he have to take with, both his Shabbos and weekday taalis, or if one is medakdek to use special Shabbos shoes, can he be lenient when traveling, we wrote; “From Shulchan Aruch (O.H. 262: 3), Mishna Berura and other Poskim it appears that there are two distinct opinions as to how to comply with the obligation to wear special and dedicated clothing in honor of Shabbos. Halachikally, it suffices if the suit and hat are used only for Shabbos, while inner garments including shirts, as long as they were washed for Shabbos, that already makes them special and dedicated. Shoes are similar, and they should be shined or cleaned. (Rav Poalim 4: 13, Yisodei Yeshurun p. 26, et. al.).
However, others assert that all clothing should be dedicated only for Shabbos use, including shoes and taalit kattan (Arizal and Mekubalim as quoted in Magen Avraham ibid. 2, Moreh Be’etzba 4: 139, Kitzur Sheloh, et. al.).” (See also questions 1147 and 844 in regards to wearing Shabbos clothing on Tisha Beav when it falls on Motzei Shabbos.
Horav Shlomo Miller’s Shlit’a opinion is that one may do as he finds most convenient. However if he undressed and went to rest before selichos, the Rov’s opinion is that he should better wear weekday clothes.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a