The Laws of The Beginning of the Month (3)

1. It is forbidden to fast on the first day of the month, and even for a significant part of the day it is forbidden to fast. (Shulchan Aruch and Biur Halachah 418)

2. It is a good thing to increase the meal of the beginning of the month and Chazal say that all of the food of each person are fixed for him from the beginning of one year to the next apart from the expenses of Shabbos and Yom Tov, the beginnings of the months and the intermediate days of the festivals when if he adds he receives more and if he spends less he will receive less. (ibid 419)