Disclaimer: This will work for stores on Miva Version 9.6 or newer. Note that this will require making template changes. Make sure you are aware of what version was active before any changes are made. These edits are low-risk but if you feel uncomfortable with making these changes then we advise you to seek help from a developer. 

Objective: Merchant needs to display the IP address on the INVC page for successful orders.

Instructions: 

The best way to capture the IP address of the customer would be to create a custom customer field with the code of "order_ip"

If you are not familar with making custom customer fields you can watch this video below.

http://docs.miva.com/videos/custom-fields-overview

Then add the following code to your INVC page: 

Code: 
<mvt:if expr="l.settings:page:code CIN 'INVC'"> 
    <mvt:item name="customfields" param="Write_Order(l.settings:order:id, 'order_ip', s.remote_addr)" /> 
</mvt:if>