Sony is incentivising the Xperia Z3+ (E6533) and the Xperia Z4 Tablet (SGP712) by offering a $50 PlayStation Store credit to U.S. residents. You're eligible to get the $50 credit if you purchase either device from Amazon or BHPhotoVideo between November 1 and December 31.
Following the purchase, you'll have to head to the dedicated offer website to redeem the PlayStation Store credit:
Customers must complete the online redemption form and upload photographs of the original sales receipt for an eligible Xperia device and the IMEI number found on the side of their Xperia device box. The redemption claim form can be found on xperiaoffer.com. All redemptions must be submitted by 11:59 pm ET on 01/31/16.
Once the redemption claim is validated, you'll receive the $50 credit via email. Interestingly, Sony's latest flagship, the Xperia Z5, is not yet available for purchase in the U.S., and it remains to be seen if the device will be added to the list once it goes on sale. Head to the link below for more details on the offer.