anchor.diff:  * The Kill Bill *External key* field should map to the unique id of the account in your system (should be unique and immutable). Kill Bill will auto-generate an id if you don't populate this field
   * There are many more fields you can store (phone number, address, etc.) -- all of them are optional. Keep local regulations in mind though when populating these (PII laws, GDPR, etc.).
   
  -=== Adding a payment method
  +=== Adding a Payment Method
   
   To trigger payments, Kill Bill will need to integrate with a payment provider (such as Stripe or PayPal). Each means of payment (e.g. a credit card) will have a *payment method* associated with it.
   
  
positive.code: = Getting started
  
  == Introduction
  
  
negative.code: * http://killbill.io/blog/[Our official blog]
  * https://www.capterra.com/p/159213/Kill-Bill/#reviews[User reviews on Capterra, a Gartner company]
  
  ==== Technical Guides
  
  To start integrating Kill Bill in your environment:
  
  