Authorize.net has an "Expanded Credit-Return Capabilities" feature that allows you to increase the 120-day window for processing refunds.
There are substantial risks involved in activating this feature. This link details the terms and agreement:
If you are an organization that is using ASAP's Authorize.Net account as a payment gateway, you'll need to refund the customer in a different manner other than credit card since we do not have the "Expanded Credit-Return Capabilities" enabled.
Other gateways have different capabilities and you'll need to research with them directly within your own account to see if you have this option available.
You can also refund your customer with a check, cash, or another payment type to avoid opening your gateway window to the expanded capabilities. You will need to do this if you are using ASAP's Authorize.Net account as a payment gateway.