USCIS online account number / USCIS ELIS (Electronic Information System)?

Go ahead and leave it blank ... the ELIS system is broken most of the time anyway.

PROFESSOR OF IMMIGRATION LAW for 10+ years -- All responses on this blog are offered for informational purposes only. It does not constitute an attorney-client relationship. Also, keep in mind that this is an INTERNET BLOG. You should not rely on anything you read here to make decisions which impact on your life. Meet with an attorney, via Skype, or in person, to obtain competent personal and professional guidance.

This may effect how you receive notice of the files progress but it will not effect the application itself.

I have more than 30 years experience and practice immigration law only. My answer to your question is general in nature and not to be construed as legal advise or as establishing an attorney-client relationship. An answer to your question posted on this site is not meant to be a substitute for a consultation. For legal advise specific to your situation Schedule a consultation by contacting my office via telephone email or comment on my website.

Yes, leaving it blank will likely have no negative effect on your I-751.

This answer has been prepared for informational purposes only. The information presented is not intended as legal advice, is not to be acted on as such, does not constitute solicitation or purport to form an attorney-client relationship, and is subject to change without notice.