iPhone 15 Plus trade-in for iPhone 15

While you can theoretically do this, WHY would you do this? You'd be getting essentially the exact same phone, only smaller and you'll lose money in the process. From what I can tell, your phone if in excellent condition is worth $430 in trade value. You can certainly use that towards the purchase of an iPhone 15, but it would make so much more sense to upgrade to an iPhone 16, which has more RAM and is capable of running Apple Intelligence, which iPhone 15 or 15 Plus cannot.

Do what's best for you, but to me, it doesn't make a lot of sense to trade a 15 Plus for a 15.

The trade in of the one phone and the acquisition of another one are separate processes. You don't trade in one for the other as such.

To get more information about the Apple Trade In service click on the link --> Apple Trade In - Apple

- Don't miss the FAQ at the very bottom.

- Start a trade-in by clicking on a device in the section "Select your device to get a trade-in estimate" - Smartphone, Tablet, Computer, Watch, Other devices (recycle only)

- The newest models may not be listed as eligible for trade-in. Contact Apple if you want to double-check. If you cannot simply return the device to Apple within the refund period (not available in all countries), you may need to see if you can sell your device as used.

- Follow the instructions included in your trade-in kit. It explains how to prepare, pack, and ship your device.

- Run your device (even damanged ones) through Apple's estimate calculator to see if it has any value. If Apple declines your device because it needs repair, trade-ins will generally not recoup the costs of repairs. Consider recycling the device as mentioned at the very bottom of the support article.

- -What if I’m not ready to buy something? No problem. We can put the value of your current device on a gift card that you can use anytime. Get an estimate through the trade-in tool and choose the Apple Gift Card option.

How to prepare your iPhone, Apple Watch, or Android for trade-in is outlined in this article

Trade in your iPhone, Apple Watch, or Android device - Apple Support

Buy iPhone - Apple

If the phone is paid for, you should be able to trade it in. See the information here, Apple Trade In - Apple