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What Is A Number? and What Is the Difference between A Number and SSN?

Hi William,

I am in H1B status. I am filing the I-140 form for my Green Card application, and I just do not know what is the A number asked in the I-140 form? I do not believe I have A number at this time. 

Also, what is the difference between A number and SSN.


The A Number is the Alien Registration Number. The “A” number is used by the Department of Homeland Security system for the purpose of identifying aliens. It alone does not serve as employment authorization nor is it evidence of legal status or permanent residency. After your I-140 approval, you will be given an A number by USCIS.

Aliens are also often confused Social Security Numbers (SSN) with alien registration numbers (or “A” number) issued by the Department of Homeland Security. An alien is issued an “A” number when he is applying for immigration, is put under removal proceedings, or under other special registration programs. 

The formal “A” number contains eight digits and will occasionally begin with a “0” and have a total of 10 digits. In general, one may only have one formal “A” number. In multiple applications cases, however, an alien may receive multiple “A” numbers. 

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