Introduction
Magento Multiple Coupons extension let your customers apply multiple coupons to increase their loyalty. It's very inconvenient for your customers to use all coupons for place several orders. Imagine, your customer has 2 coupons: 20% Magento discount code on every piece and 15$ flat discount. If he wants to make a significant purchase, he will be happy to use both coupons at once, while you’ll get a loyal customer as a result.
The extension page: http://store.magenest.com/magento-extensions/multiple-coupons.html
Requirements
Your store should be running on Magento Community Edition version 1.6.0 and earlier.
Configuration