Can I trade in an iPhone with a cracked rear screen?

You can try, but you're unlikely to get much if anything for it. They cancelled an iPad trade-in for me when the device was in perfect cosmetic condition and working perfectly because (they said) of some pixel damage on the screen display. So good luck!

When you are buying a new phone on the Apple website, there will be an option for iPhone trade in. You simply select the dropdown selections of what type of iPhone you have, and the condition of the phone, depending on the condition, Apple will give you an estimate for how much you can trade in your for for. If it says "Your smartphone is ready to recycle with Apple Trade In." then your phone is not worth anything for trade in.