anchor.diff:  
   ==== Refund
   
  -Here is how a payment, followed by a refund would look like:
  +A payment followed by a refund would look like this:
   
   [cols=4, options="header"]
   |===
  
positive.code: Payments can be made against existing invoices, either automatically by the system or manually by leveraging our apis. Kill Bill allows to have multiple partial payments against a given invoice, but the reverse -- i.e one payment spanning multiple invoices is not (yet) supported.
  
  One Payment against one invoice is the default model, and this happens automatically by the system provided the customer `Account` has a valid default payment method - in which case it used to make the payment. However, one can customize the system on a per `Account` level to disable this behavior, using the following mechanisms:
  
  * `Account` does not have a default payment method -- the system will abort the payment.
  * `Account` has been tagged with one of the following:
    ** `AUTO_PAY_OFF`: Prevent system from making automatic payments
    ** `MANUAL_PAY`: Prevent system from making automatic payments and we expect those payments to happen outside of the Kill Bill system -- e.g checks.
  
  Anytime an `Account` has a positive balance, i.e. at least one `Invoice` was not (partially) paid, one can use our apis to issue a manual payment against such invoice. Based on what we said earlier, such situation can occur if the system was configured to not make payments or in cases where a payment was issued but failed. 
  
  
  The call below illustrates how to make such a payment -- against an existing unpaid invoice `99f91a42-a83f-4d59-b337-9df1b53f79b1`:
  
  [source,bash]
  ----
  
negative.code: 
  ==== Chargeback
  
  Finally, a payment followed by a chargeback would look like this:
  
  [cols=4, options="header"]
  |===
  