The priority date determines your place in line/the queue. The priority date, according to the USCIS, is normally that date when the relative or employer of the applicant files the immigrant’s visa petition with the USCIS. You should be able to locate the priority date on the Notice of Action (Form I-797) which was filed on behalf of the applicant. The USCIS officer should verify the priority date “by reviewing the actual immigrant petition or permanent labor certification application.”