💳 Apple Pay
What it is
Apple's card-payment sheet (PKPaymentAuthorizationController) for charging real money to a card — completely separate from In-App Purchase. You need a Merchant ID (merchant.com.yourname.app), a payment-processing certificate, and a processor (Stripe, Adyen, Braintree) to actually settle the charge. Apple takes no cut of Apple Pay transactions.
When you need it
For physical goods and real-world services: e-commerce checkout, food delivery, bookings, donations to registered nonprofits. The inverse of IAP — using Apple Pay (or any external payment) for digital content violates 3.1.1, and using IAP for physical goods violates 3.1.3(e)/3.1.5.
Setup, review rules & privacy labels — Pro
Per-stack setup instructions, App Review rules, and privacy-label mapping are part of the full reference.