If you have to file a paper document with the IRS and you want to absolutely avoid delivery problems, you need to do one of two things:

Mail your document on or before the due date using registered or certified mail.

Send your document to the correct IRS address on or before the due date using an IRS-approved delivery service.

Registered or Certified Mail

As you can see in It’s Tax Filing Season—Mail Correctly to Avoid IRS Trouble, your use of registered or certified ... Log in to view full article.