Apple is now offering a kind of rebate for customers who had their iPhone 6 or later devices battery’s replaced. Those who had out-of-warranty replacements between January 1, 2017 and December 28, 2017, is entitled to a $50 credit.
The credits will be handed out via electronic funds transfer or as a credit on the credit cards used to pay for the battery replacement service. Only replacements completed at an Apple authorized service location (Apple Store, Apple Repair Center, or an Apple Authorized Service Provider) are considered eligible.
Apple will contact eligible customers via e-mail between May 23, 2018 and July 27, 2018, with instructions on how to obtain the credits. For those who do not receive an e-mail by August 1, 2018 but is eligible for the credit offering, you can contact Apple here by December 31, 2018. For those who will contest their eligibility, proof of service from an Apple authorized service location may be required.
Again, these are only for out-of-warranty battery replacements, those who had in-warranty replacements during the said dates are ineligible.