If you are an immigrant and have traveled outside of the US, you will usually need Advance Parole (USCIS Form I-512) to re-enter the US and to protect your immigration status. This is especially important if you have pending applications for changes in your status or for benefits. If you leave without filing Form I-512 correctly, the USCIS will automatically consider that you are abandoning your applications when you leave the country. This means that you will not be able to re-enter the US.
It is vital to apply for Advance Parole if you are considering leaving the US. Even a trip to Mexico, the Bahamas, or just across the border to Canada can affect your application and can make it impossible for you to re-enter the US. Since you will not be able to appeal or enter the US, you must apply for Advance Parole – and receive it — before you exit the US. Once you leave the country, it is too late. Just filing for Advance Parole is not enough. You must have documented proof that your application has been accepted and is complete before you leave the country.
Advance Parole (USCIS Form I-512) is designed to help immigrants leave the country for personal or business reasons without losing their status application. For example, if you are applying for a green card but face a family emergency that requires you to leave the US, you can leave the US to deal with your family emergency and still be able to re-enter the US – as long as you have your I-512 status first.
You will only need Advance Parole if you have filed Application for Adjustment of Status and need to leave the country. If you have a valid visa or green card, you will not need to file Form I-512.
There is one important exception to this rule if you have been in the US illegally for more than 180 days, you cannot apply for Advance Parole and you cannot leave the US while waiting to hear about your Application for Adjustment of Status. You may even receive an Advance Parole if you apply for it, but once you leave the US you are automatically banned from re-entering the US for 3-10 years under § 212(a)(9) of the Immigration and Nationality Act. Therefore, if you have been in the US illegally, getting Advance Parole alone may not be enough to secure re-entry into the US.