I mailed my extended 2018 Form 1040 on 10/5/19 using certified mail return receipt requested. Surprisingly, on 10/7/19 I received the return receipt back in the mail but it was not stamped as received by the IRS. Is the purchase receipt and the unstamped return receipt adequate documentation to prove timely filing or do I need to do anything else?
Go to the USPS Tracking web site. Enter the certified mail number and print the tracking results. It will show when the envelope was delivered.
(It sounds like the return receipt fell off the envelope somewhere in the post office and got sent back to you. There's no way that it got to the IRS and back to you in two days.)
you could call the IRS to see if they have received it but processing a paper return could take 6 weeks. it could as of this date still be in transit.
First choose your language.
You should then be transferred to an agent, but there is likely to be a long wait.