If you received an official letter from the IRS you will need to mail these documents to them.
It is not uncommon for the IRS to request additional information. Google the letter's return address and only mail information to an official IRS address. You can call the IRS to verify. 1-800-829-1040.
Also, if you set up an online account with the IRS, you can communicate with them there and verify this letter.
Click
here to find where to mail your Federal return from your state: https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment