If a donation in RaiseDonors has an error from Authorize.net similar to,
Error 11: A duplicate transaction has been submitted.
A transaction with identical amount and credit card information was submitted within the Duplicate Transaction Window. The error indicates that a transaction request was submitted within a few minutes of a previous attempt with the same information. Authorize.Net identifies duplicate transactions by matching the data provided with the transaction.
You need to modify the "Duplicate Window" setting in RaiseDonors. To do so, log into RaiseDonors and goto your merchant settings page here. From there, supply a lower or higher value in the "Duplicate Window" section.
The largest value we will accept for duplicate window is 28800, which equals eight hours. If a value greater than 28800 sent, the payment gateway will default to 28800. If duplicate window is set to 0 or to a negative number, no duplicate transaction window will be enforced in Authorize.net. If no value is sent, the default value of 120 (two minutes) would be used.
For example, if you wished to set a duplicate transaction window of five minutes, you would set duplicate window to 300, as there are 300 seconds in five minutes.
Note - if you are in a situation to manually create recurring schedules, having multiple schedules per donor, there is logic at Auth.net that checks for duplication. These settings are unfortunately, not customizable.