QuickBooks (Intuit) Payment Gateway provides an easier, cost effective and simple alternative for a small business for accepting credit cards.
And this OpenCart Plugin allows you to accept credit card payments on your site through QuickBooks(Intuit) Merchant Account.
Documentation is located at http://www.patsatech.com/docs/quickbooks-intuit-payment-gateway
[box type="note"]Important Note: This Gateway Implementation Requires the cURL to Enabled on your Hosting Account and also make sure your site is SSL enabled.[/box]