We are having an issue where the customer receives payment transaction error with the reason of "Invalid amount for capture" in Authorize.net payment gateway in Magento.

Some customers have been persistent and their order finally goes through after attempting to place the order several times, but we are also losing sales. It appears that if the customer logs off and logs back in it allows them to place the order but not entirely sure of this as it has only been attempted with several customers. This problem started when we moved servers. I have attached a one sample emails of the failure reminder.

Reason Invalid amount for capture.

Checkout Type : onepage

Customer: XXXXXXXX

Total: USD 36.27

Billing Address: XXXXXX

Shipping Address: XXXXXXX

Shipping Method: free US shipping over $75 // USPS Priority Mail

Payment Method: Credit Card

Date & Time: Oct 5, 2014 7:39:22 PM

3 Answers 3


I found that when I had this happen I had to adjust my Authorize.net configuration. This article did the trick for me, even though it might not be exactly your issue.


  • Just want to add some info to this post, I encountered this same issue for a client's site and the problem was that both the AW_Sarp2 extension and another extension were rewriting Mage_Checkout_Model_Type_Onepage. I had to modify one of the two third party extensions to extend the other (as AheadWorks was not being used, which is what caused the exception being thrown) Feb 17, 2016 at 20:15

You need to comment in a file app/code/core/Mage/Paygate/Model/Authorizenet.php following code

if ($this->_formatAmount(
     $cardsStorage->getProcessedAmount() - $cardsStorage->getCapturedAmount()) < $requestedAmount
 ) {
     //Mage::throwException(Mage::helper('paygate')->__('Invalid amount for capture.'));
$CreditCardAmount=number_format($amount, 2, '.', '');
$transactionRequest = new AnetAPI\TransactionRequestType();

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