Customer was Allowed To Check Out with Invalid Zipcode

[dlovin123]

I customer put in an invalid zipcode.  They put in SS059  instead of 33059 .  Somehow it stll allowed them to complete the checkout process. I tried to duplicate this but it stopped me from checking out.

The other issue is that it failed to charge her any shipping. The shipping doesn't even show up on the order. It's blank.

Any ideas or thoughts on what I should check first?

[GauravMehta04]

Yes do check zipcode on billing and shipping steps, use event observer Or overright onepage controller and get user entered zipcode and do validated with possible zipcode it valid then customers go ahead otherwise redirect them into cart page with proper error message.

Event Observer E.X:

<events>
	<controller_action_predispatch_checkout_onepage_saveBilling>
		<observers>
			<savebilling>
				<class><modulename>/observer</class>
				<method><your method name></method>
			</savebilling>
		</observers>
	</controller_action_predispatch_checkout_onepage_saveBilling>
</events>	

override controller;

http://www.amitbera.com/how-to-override-a-controller-in-magento/

Hope it helps you