Each fiscal year (October 1 through September 30), the U.S. government sets a numerical limit on how many Green Cards will be issued. Retrogression occurs when more people apply for a visa in a particular category or country than are available for a given month. This results in a quota backlog. No one country may have more than a specific percentage of the total number of visas available to it annually. If these limits are exceeded in a particular category or for a particular nationality, a waiting list is created and applicants are placed on the list according to the date of their case filing. This date is called a “Priority Date.”
According to U.S. Citizenship and Immigration Services (USCIS), “Generally, the priority date is the date when the immigrant petition is properly filed with USCIS. In some instances, the priority date is when the labor certification application was accepted for processing by the Department of Labor.”
For the employment-based category which requires labor certification (EB-2 and EB-3; see previous article), the priority date is established on the date a labor certification is filed with the U.S. Department of Labor. If your category is employment-based but does not require a labor certification, then the priority date is established on the date USCIS receives the I-140 Immigrant Visa Petition. However, the priority date does not attach to your case until the I-140 has been approved.
In order for an individual to obtain a Green Card, a visa number must be available. This is referred to as the priority date being “current.” The priority date is current if there is no backlog in your employment-based category, or if the priority date is before the date listed as current in the State Department's monthly Visa Bulletin.
The Department of State publishes a monthly Visa Bulletin which lists the cut-off dates that govern Green Card availability. The monthly Visa Bulletin determines which applicants are eligible to file for adjustment of status, as well as which applicants are eligible for a grant of permanent resident status. Usually the cut-off dates on the Visa Bulletin move forward in time, but not always. Demand for visa numbers by applicants with a variety of priority dates can fluctuate from one month to another, with an inevitable impact on cut-off dates. Such fluctuations can cause cut-off date movement to slow, stop, or even retrogress.