Hey, @mohit2002!
Thanks for clarifying and sharing their reply.
Since neither Woo nor AvaTax should do this, there might be something else interfering to add the column when AvaTax is active.
Can you please run a conflict test to see if this happens when only Woo and Avatax are active?
To test, you’ll first want to change the theme on your site to Storefront, then you’ll want to deactivate all plugins except for WooCommerce and AvaTax and take a look. If that fixes the problem, re-enable the other plugins one by one (gradually), checking after each, to see where the issue is coming from.
— Be sure you have a good backup in place of your full site and database. You can ask your host for backup functionality or you can consider using a service like Jetpack. If something goes wrong, you will be able to restore it.
— It is important to consider as well a staging functionality in case you would not like to touch your production site (you can ask your host if they offer this service), or you can use WP Staging for quickly spinning up a new test site.
You can find more about this in this guide.
Please let us know about your findings.
Have a wonderful day!