If I sell my iPhone, how will the warranty be affected?

I recently dropped my iPhone 4 in the bath. Whoops...

Knowing Apple's stance on water damage, I simply upgraded (I was due an upgrade as part of my contract) and got a new phone.

My house-mate then informed me that I could go to Apple and purchase a new phone for £119. I did just that, and the kind lady in the Apple store let me know that the new phone only comes with a 90 day warranty.

As such, I have two Apple phones, and I'd like to sell my old (but brand new..) iPhone 4.

My question is: if someone purchases my phone on say eBay, will they too receive the 90 day warranty, or does it become invalid when I sell the phone?

The original warranty usually the standard 1 year + any AppleCare stays with the iPhone. And any remaining warranty transfers to the new owners.

Apple Care FAQs

Is the AppleCare Protection Plan transferable?

Yes. If you choose to sell or give away your Apple product, you can also transfer the ownership of the AppleCare Protection Plan. Please see the AppleCare Protection Plan Terms and Conditions for complete details.

If you bought the iPhone 4 new through the Apple Store or a Cellphone store, it comes with a one year warranty, not a 90 day warranty. This applies in The UK as well as in the US.

As per the iPhone 4 warranty:

Apple warrants the Apple-branded hardware product and accessories contained in the original packaging ("Apple Product") against defects in materials and workmanship when used normally in accordance with Apple's published guidelines for a period of ONE (1) YEAR from the date of original retail purchase by the end-user purchaser ("Warranty Period"). Apple's published guidelines include but are not limited to information contained in technical specifications, user manuals and service communications.

The date of purchase is tied to the serial number at the point of sale. Your eBay purchaser will have the remaining balance of the one year warranty. They can check the status of the warranty at: https://selfsolve.apple.com/agreementWarrantyDynamic.do

In short, yes, they will have the warranty, but the warranty does not "start over" when the buy it, they only get the remaining balance.

If you have AppleCare Plus, it must be manually transfered by calling Apple's 800 number. AppleCare Plus can only be transferred ONE time. (The purchaser could not transfer it a second time)