For the sake of confidentiality, can my joint sponsor's i-864 be mailed/submitted separately from my i-485?

[sslagt 0]

My joint sponsor (employer) does not feel comfortable providing me with all his tax documents and income information. Can he send his i-864 to USCIS independently? If so, how would we go about this?

If not, would we be able to include a closed envelope in my application that has his i-864 in it, perhaps with a letter explaining the situation?

[Pitaya 2,577]

Welcome to the forum.

You could likely send the cosponsor's paperwork in a separate sealed envelope, clearly marked with contents and proper identification, and include that sealed envelope with your AOS application and paperwork. To send it in separately is just asking for potential troubles, like not being matched up with your paperwork and/or just plain lost.

Good luck on your immigration journey.