Form 706 estate tax return packages returned If your Form 706 package was returned to you, you must take specific action to ensure your package is considered timely filed. Taxpayers or tax professionals can use certain private delivery services designated by the IRS to meet the "timely mailing as timely filing/paying" rule for tax returns and payments. These private delivery services include only the following: DHL Express: DHL Express 9:00 DHL Express 10:30 DHL Express 12:00 DHL Express Worldwide DHL Express Envelope DHL Import Express 10:30 DHL Import Express 12:00 DHL Import Express Worldwide FedEx: FedEx First Overnight FedEx Priority Overnight FedEx Standard Overnight FedEx 2 Day FedEx International Next Flight Out FedEx International Priority FedEx International First FedEx International Economy UPS: UPS Next Day Air Early A.M. UPS Next Day Air UPS Next Day Air Saver UPS 2nd Day Air UPS 2nd Day Air A.M. UPS Worldwide Express Plus UPS Worldwide Express The private delivery service can tell you how to get written proof of the mailing date. Street addresses of the submission processing centers for delivery by a PDS