+To settle an authorization-only transaction (where you set action to
+'Authorization Only'), submit the nine-digit transaction id code in
+the field "order_number" with the action set to "Post Authorization".
+You can get the transaction id from the authorization by calling the
+order_number method on the object returned from the authorization.
+You must also submit the amount field with a value less than or equal
+to the amount specified in the original authorization.
+
+Recently (February 2002), Authorize.Net has turned address
+verification on by default for all merchants. If you do not have
+valid address information for your customer (such as in an IVR
+application), you must disable address verification in the Merchant
+Menu page at https://secure.authorize.net/ so that the transactions
+aren't denied due to a lack of address information.
+