Real One Page Checkout introduces a serious problem with Address records

Using your plugin, I had a problem with my taxation, it was always coming up zero for any Customer who hits your One Page cart page. The plugin creates BLANK, null records in the Address table and associates them with the Customer. Any subsequent carts will refuse to display tax, not certain what else might be the result. I've not been able to use the plugin for our store because of this bug. I tried to document this with your staff and they essentially refused to do anything about it unless I gave them admin access to my store. It's not necessary to gain access to my store, you can test the issue yourself. http://stackoverflow.com/questions/31633500/nopcommerce-3-6-tax-by-country-state-zip-always-results-in-zero-tax

Hi,

We needed the admin credentials so we can see your settings and replicate them, because we were unable to reproduce the problem. 
Now, because of the screenshots that you have posted in StackOverflow we were able to replicate your settings and we have tested the plugin with them. Again, there doesn't seem to be any problems. See the bellow screenshots.

Customer with test address
Order made with this test address

As you can see the test address has the same zip, state and country as the one that you have provided in StackOverflow. The tax settings are the same, only the percentage I have set is different to be more noticeable.

Do you have any modifications to nopCommerce source code ? Also, we still need admin credentials so we can investigate other possible reasons for the issue, but we can not guess your settings.

P.S.
If you don't see the tax on the Checkout page it is because you need to fill the shipping address fields that you have set in the tax configuration settings.

Checkout page

Keep in mind that if you want to always see the tax you will need to set your default tax address from Tax Settings.

Example for default tax address

Looking forward for your response!