Normally the Bill To section of the checkout is optional if left blank. If the Bill To fields are now being required even when left blank, this is usually caused by a mis-configuration in the Miva Merchant States list, caused by deleting the "Outside US" option from the list. The mis-configuration is usually due to some merchants not wanting to ship to places outside of the United States. So, they simply remove it.
The "Outside US" option is required for the optional Bill To section to work correctly. It does not need to be called "Outside US" if you do not ship outside of the US, you may re-label it is as something like "Select State" if you prefer. Miva Merchant needs at least one item in this list, without a CODE to complete the order form and leave the Bill To side empty.
Please follow these steps to correct this issue:
1. Log in to your Miva Merchant administration interface.
2. Expand the "Stores" menu by clicking the blue triangle.
3. Expand your store by clicking on the blue triangle next to the store name.
4. Click the menu selection: "States."
5. In the main page, click "Add State." It is a yellow button in the upper-right corner of the page. It will show "Add State" if you hover over it with your mouse pointer.
6. It will open two text fields. One will be labeled "Code" and the other will be labeled "State." Leave the text field under "Code" empty, and type something like: "Select One" or "Choose a State" in the field labeled "State."
7. Click Update.
That should fix the order form so that "Bill To" no longer must be filled out. If the problem still persists, please contact Miva Technical Support.