Magento and Authorize Suspected Fraud Credit Memo

When you run payment update if you do not get transaction id in your magento, have you checked transaction id created in authorize.net merchant admin? if you got in authorize.net then also it can be helpful.

if you got transaction id in your authorize.net merchant center than also by specifying extra variable or might some code change can solve your problem.

I had faced same type of issue in another payment module named Klarna and I resolved it by overwrite method and add one extra text field where I specified invoice Id generated in klarna to create online creditmemo.

In your above scenario there is some more question arise.

1. Your authorize.net set in which mode? authorize or authorize and capture?
2. When authorize.net returns suspected fraud code at that time it actually capture the payment from customer or not? if not capture payment it should not generate invoice.
3. When authorize.net approve transaction and you run get payment update your order state change to processing but at that time do you get any transaction_id in your response or not. if you get and your invoice already generated might you need to update your invoice and fill the transaction_id pragmatically if you want to create credit memo online by using same authorize.net.

The easiest solution is to refund off-line if this happen rarely. to refund payment off-line and on-line also there is different way check below link for details Credit memo vs Refund Which one is true? Magento 1.9