How do I create Apple Pay invoices?

There is not such thing as an Apple Pay invoice. If you’re thinking of using Apple Cash for commercial (business) transactions, it’s prohibited by the terms and conditions of Apple Cash. Green Dot Bank, issuer and servicer of Apple Cash accounts, will close and permanently lock both parties accounts. If you’re a legitimate business open a merchant account so you can accept Apple Pay and other payment methods.

https://applecash.greendot.com/termsconditions/

Payment Platforms - Apple Pay - Apple Developer