It depends on how long it takes to get a signature fromthe customer certifying that the letter has been recieved. The mail carrier cannot deliver the letter until a signature is obtained to certify that the letter was received and the date it was received. This can take time. If the recipient is not home to sign for the certified letter, the carrier leaves a notification. The customer can then arrange for the letter to be redelivered when they are going to be there to sign, or request that the letter be held at the PO so that the customer can come in and sign for it and pick it up at the office. If the customer is at home when the first delivery attempt is made, they can sign for it and get it then. If the customer is not available to sign for the mailpiece, a notification is left so the customer can call the office to arrange for delivery when they will be there to sign, or arrange to have it held at the office so they can come in and sign for it. Once the customer has signed for the letter the green card will be sent back to the sender. The time depends on how long it takes to get the signature.