Ok, I keep seeing this over and over in the threads, and I keep seeing WRONG info being spread around. So, allow me to present my: 100% accurate, 100% complete, no nonsense guide to selling an iPhone you bought to sell. This isn't a debate about whether you SHOULD be selling the phones, this is just information that will INEVITABLY help the buyer of your phone. If you bought your phone from Apple.com and had it SHIPPED to you, AND you paid full price: If the phone is T-Mobile, there's nothing special to do. Print a copy of the original invoice for the buyer so they can prove ownership, and sell the phone. If the phone is Verizon, Sprint or AT&T: **STOP** You can NOT sell it without first opening the box and turning on the phone, and completing the initial verification. Apple official support document https://support.apple.com/en-us/HT203304 explaining the reasons... Also, once you complete the verification, the *now active SIM on your account* is the one in the new phone. Don't bother removing it first, it won't matter. The phone was sold as a replacement device on your account, and the carrier WILL swap the active SIM to the sim in the phone when it shipped. So, remove that SIM *AFTER* you've gone through the initial activation screen. Don't log into your iCloud account, etc, just skip all setup questions, then, go to Settings, General, Reset, Erase all Content and Settings. Once you've done that, turn the phone off, remove the SIM, package the phone back up, and sell it. Include a copy of the original invoice with the phone. If you bought your phone AT an Apple retail store, AND you paid full price: Sell the phone. Include a copy of the invoice with the phone. If you bought the phone from a Carrier store that ISN'T Verizon: You must first unlock the phone with your carrier. Then, sell the phone with a copy of the invoice. If you bought the phone FROM VERIZON: The phone is already unlocked. Sell it with a copy of the invoice. Bought the phone ANYWHERE ELSE? The phone follows the activation profile of how it was originally turned on. Ensure you FIRST install a Verizon SIM into the device, then power it on and activate it. Reset the phone after, and remove the Verizon SIM. If you boot the phone with an AT&T, Sprint, T-Mobile or any other SIM, the phone WILL BE locked to that carrier. Unlock it first, then sell. Include a copy of the invoice with the phone. I hope this helps.. This is from YEARS of experience, and carefully studying what happens when you buy iPhones in a variety of ways. This IS accurate, and failure to follow the directions WILL result in VERY upset buyers.