Let’s say I’ve added a product to my cart, and I am now checking out. I am now on the Billing & Shipping page, and I enter all necessary information *except* a ZIP Code. If I now click Proceed with purchase, I am taken to the Review & Payment page. Only after I have entered my credit card info and clicked the Place order button do I see an error message about the missing ZIP. Now I have to go back a page, enter the ZIP, and proceed. This seems non-intuitive, especially for less tech-savvy customers.
Is there any way to prevent the customer from proceeding to the next step if a required field is empty?