Magento - Enable or Disable Coupon Code Form in Shopping Cart

If you would like to disable the coupon codes from the shopping cart in Magento perform the following steps:

go to /app/design/frontend/base/default/layout/checkout.xml

and comment out the following line:
<block type="checkout/cart_coupon" name="checkout.cart.coupon" as="coupon" template="checkout/cart/coupon.phtml"/>



You can also comment out the line below it if you would like to remove shipping calculations from the shopping cart. Use <!-- these opening and closing tags to comment them out -->

For example:
<!-- <block type="checkout/cart_coupon" name="checkout.cart.coupon" as="coupon" template="checkout/cart/coupon.phtml"/> -->

If you would like to enable them remove the comment tags!