Question: I forgot to prepare shirts and polish my shoes before the nine days. What can I do?
Answer: The Gemara (Taanis 26b; 29b) writes that one mustn’t clean or iron one’s clothes during the week of Tisha B’av. The Rema (OC 551:3) writes that the custom (for ashkenazim) is not to do so for the nine days from Rosh Chodesh Av. The Rema (OC 551:14) writes that one may wash a child’s clothes, especially if they regularly get them dirty. Some (Piskei Teshuvos 551:n232) write that this only applies to younger children’s clothes and the Mishna Berura (551:82) writes that one shouldn’t wash their clothes in the week of Tisha B’av.
Additionally, one isn’t supposed to wear freshly washed clothing. The poskim write that this doesn’t apply to clothing that are worn on the skin and changed daily. Thus, while most poskim write that this prohibition applies also to shirts, R’ Chaim Pinchas Scheinberg (quoted in Divrei Chachamim OC:459) held that one can wear fresh shirts, too. One who is particularly bothered by not changing their shirt may do so (Piskei Teshuvos 551:17).
While the Rema (OC 551:1) writes that one shouldn’t even wear one’s Shabbos clothes on Shabbos Chazon, most people follow the Vilna Gaon (OC 551:3) who allows wearing fresh clothing even when Tisha B’av itself falls on Shabbos (See Aruch Hashulchan OC 551:11). The Mishna Berura (551:33) writes that one shouldn’t change one’s bedding though.
Similarly, one is allowed to polish one’s shoes for Shabbos (Igros Moshe 3:80; Rivevos Ephraim 1:375).
The Kaf Hachaim (OC 551:91) and Piskei Teshuvos (551:17) write that it is advisable to prepare for the nine days by wearing one’s fresh shirts for a while (See Shach YD 389:4).
R’ Betzalel Stern (Betzel Hachachma 4:138) writes that if one forgot to prepare shirts before Rosh Chodesh, one can change shirts a few times on Shabbos, thereby having almost fresh shirts to wear after Shabbos (See Kaf Hachaim ibid).