iOS app store falsely claims I have no payment method while gifting app I want to gift an app from the iOS app store. I verified I have enough prepaid store credit, set up the gift purchase, and clicked the Buy button.

The iOS App Store gives a false error message:


  Payment Information Required
  
  A method of payment is required to buy an iTunes Gift. You can add a
  payment method from your Account Information Page.


I checked my account information and it has enough prepaid store credit to buy the app as a gift.

What's causing this and how do I fix it?
I called Apple Support and apparently prepaid codes (store credit) can't be used to buy gifts, although this restriction isn't documented anywhere. Posting this answer for everyone to know.

To gift apps without a real debit or credit card: most convenience stores and malls offer special prepaid cards that behave like debit or credit cards. You can buy one of these, plug them into your account as a "debit" or "credit" card, and use that instead.