IV Availability
The issuance of family sponsored and employment based preference visas is numerically limited by Congress. Interviews for applicants in these categories are scheduled when the applicant’s priority date becomes current and visa numbers are available. However, priority dates may change, and it is possible that at the time of the interview, visa numbers may no longer be available. If visa numbers are no longer available for your visa category, your interview will proceed as scheduled, but your visa not be issued until the priority date again becomes current and new numbers are available. Applicants should check the Visa Bulletinon the Department of State’s website for up to date information on priority dates for all immigrant visa categories.
For information on sponsoring family members for immigrant visas, USCIS provides extremely useful with more information.