Delivery time depends on whether you chose to send the Certified Mail letter via First-Class Mail or Priority Mail®. When sending via First-Class, it usually takes two to five business days. Sending via Priority Mail shortens the mailing time to two to three days. But delivery is only half the process. Key to Certified Mail® is how long it takes to receive back the all-important signature confirmation after the Certified Mail letter has been delivered, because without the signature important legal and business processes can't move forward.
For users of the traditional Green Card (USPS PS3811) the wait is normally three to five days. But as frequent Certified Mail® users can attest, there's a considerable risk that the Green Card gets lost on the way back, by accidentally getting co-mingled with other mail or getting damaged. That can result in a second piece of Certified Mail® having to be sent which creates a substantial delay.