When your petition is approved you will be given two key numbers. The first is your ‘A’ number, the number that will ultimately track with your case and end up on your green card. This number can be found on your approved petition. Secondly you will have a NVPC case number. Your case number is the number that the Embassy will reference when processing your K1 visa application. As with all reference numbers it is a very good idea to double-check these numbers on any correspondence to make sure it has been copied correctly since a typo could result in an unnecessary delay in your case.

K1 Fiance Visa Guide