Knowledgebase
How to set a minimum order amount in Magento
If you want to, in Magento you can set a minimum order amount so that customers cannot place an order that has a subtotal (after discount is applied) of less than a specified sum of money. For example, you may want to disable orders that are less than $10. To do this log in to the admin panel of your Magento and go to System menu>Configuration>Sales button in the Sales section on the left>Minimum Order Amount panel on the right.
In the Minimum Order Amount panel set the Enable drop-down menu to Yes. In the field for Minimum Amount type the number that you want to be the minimum order amount. In the text area for Description Message you can type some message to be displayed on the shopping cart page when the subtotal is less than the specified minimum amount. If you don't type any message, the default one will be shown: Minimum order amount is (followed by the specified minimum sum). In the text area for Error to Show in Shopping Cart you can type an error message. That error message will be shown when the customer clicks on the Checkout link in the header of the site or in the shopping cart sidebar. If the current subtotal is less than the minimum amount, the customer will not be redirected to the checkout page but will be shown the shopping cart page with the specified error message displayed at the top. If you don't type an error message, the default message will be shown: Subtotal must exceed minimum order amount. When you're done with the settings don't forget to click on the Save Config button.
In addition to setting a minimum order amount you can also set a minimum quantity that customers are required to order from a particular product. For more information check out the article on setting a minimum product quantity allowed in the shopping cart in Magento.