http://www.travel.state.gov/pdf/Immi...ation%20of.pdf
1. HOW THE SYSTEM OPERATES:
At the beginning of each month, the Visa Office (VO) receives a report from each consular post listing totals of documentarily qualified immigrant visa applicants in categories subject to numerical limitation. Cases are grouped by foreign state chargeability/preference/priority date.
No names are reported. During the first week of each month, this documentarily qualified demand is tabulated.
VO subdivides the annual preference and foreign state limitations specified by the INA into monthly allotments. The totals of documentarily qualified applicants which have been reported to VO, are compared each month with the numbers available for the next regular allotment. The determination of how many numbers are available requires consideration of several of variables, including: past number use; estimates of future number use and return rates; and estimates of Citizenship and Immigration Service demand based on cut-off date movements. Once this is done, the cut-off dates are established and numbers are allocated to reported applicants in order of their priority dates, the oldest dates first.
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VO attempts to establish the cut-off dates for the following month on or about the 8th of each month. The dates are immediately transmitted to consular posts and Citizenship and Immigration Services (CIS), and also published in the Visa Bulletin and online at the CA Web site (
www.travel.state.gov). Visa allotments for use during that month are transmitted to consular posts.
CIS requests visa allotments for adjustment of status cases only when all other case processing has been completed.