Q. If just a bit of the chala or the matza is missing or broken off, is it still shleimim? How much?
A. Horav Shlomo Miller’s opinion is to follow the Shaarei Teshuva (274: 1) who quotes the view of the Rosh that if the missing or broken off small piece of bread is less than one forty eight of the bread, it is not considered incomplete. However, Shaarei Teshuva quotes other dissenting opinions.
On question 245 we wrote: It has become an accepted practice to re-bake or flame the edge of a broken matza to turn it into a shleimo (Seder Haoruch 22, 4 – Maadaney Yom Tov ch. 122 – Palgey Mayim 21 – Sidur Pesach Kehilchoso p. 22). Poskim disagree as to how much of the matza should be missing to make this necessary, also if the roundness of the matza has to be restored and if it can be done on Yom Tov (Shaarey Teshuva 274,1 – Maadaney Yom Tov ibid.).
See also Shemiras Shabbos K. (8: 7) in regards to the removal of the bakery label affixed or pasted to the chala. He rules it should be removed complete, to avoid tearing the letters on the label, even if some of the crust of the bread will also be excised.
The Rov recommended to take off the label after reciting the brocho.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a