In the Beis HaMikdash, Rosh Chodesh was a day for communal attonement offerings. Since the 16th centry, Jews have observed - a Yom Kippur Katan [Minor Day of Attonement], instituted by the kabbalist of Safed, on Erev Rosh Chodesh of most months. Over the centuries, this custom fell into disuse in many communities.
Today, observance of Yom Kippur Katan is increasingly widespread. Though fasting is not common, the special prayers have been implemented by numerous congregations during Minchah to afford every individual the opporunity to refelect and recommit to appropriate life goals.
A companion to the Artscroll Siddur, the full Yom Kippur Katan service, appropriate to both Ashkenaz and Sefard congregations, is now available in booklet form. Instructions outlinig the proper order for the prayers are included in the commentary.