See the message below in immigrationportal.com. Will putting in same A# lead to transfer of case & interview? I remember Xiaobaitu says that leaving A# BLANK will have that consequence.
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ginnu
Registered User
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that is his openion law does NOT say that one cannot have more than one I-485 pending. if a person has two I-485 pending with same A# then the USCIS will transfer the case for Interview to local USCIS.
Read the full document to understand
HOW THE USCIS APPROVE I-485 full proceess MASTER DOCUMENT for INS officers:
http://www.ilw.com/lawyers/seminars..._citation2b.pdf
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Message can be found bottom of webpage:
http://72.14.253.104/search?q=cache:2tmGzMvvhLwJ:boards.immigrationportal.com/showthread.php%3Fgoto%3Dlastpost%26t%3D146754+%22multiple+I-485%22&hl=en&ct=clnk&cd=3&gl=us