I did use a separate envelope for the federal tax return forms. I mailed it to the following address according to what turbotax told me.
Department of the Treasury
Internal Revenue Service
Fresno, CA [social security number removed]
I was claiming the US-China tax treaty as a student, following the instruction from this post. Should tax returns filed with Miscellaneous Income, 1099-A go somewhere else?
Also, to follow up on contacting IRS: similar to what others are reporting in this post, it is extremely difficult to talk to someone through [phone number removed]. Can I figure out whether IRS has received the mail (delivered in February 2020) by calling a local IRS branch? At minimum, there are a lot more numbers to try 🙂
