Siman 417
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א רֹאשׁ חֹדֶשׁ מֻתָּר בַּעֲשִׂיַּת מְלָאכָה, וְהַנָּשִׁים שֶׁנּוֹהֲגוֹת שֶׁלֹּא לַעֲשׂוֹת בּוֹ מְלָאכָה הוּא מִנְהָג טוֹב. הַגָּה: וְאִם הַמִּנְהָג לַעֲשׂוֹת מִקְצָת מְלָאכוֹת וְלֹא לַעֲשׂוֹת קְצָתָן, אַזְלִינָן בָּתַר הַמִּנְהָג (בֵּית יוֹסֵף).
1 Contains 1 paragraph: On the beginning of the month, it is permitted to do work. However, those women who follow a custom to not engage in work [are following] a good custom. Rema: And if the custom is to do some kinds of work and not to do some [other] kinds of work, we follow the custom.