Shipping and tax calculation fails, when customer is using VPN

We have 4 scenarios to calculate shipping and sales tax. Orders from Germany, EU, International and Canada.
Germany has staggered shipping and sales tax, EU has just sales tax, International has neither, Canada as sales tax and shipping with different rules.

Initially the cart determines by IP where the customer is located and displays sales tax and shipping accordingly on the cart page.

If a customer uses a VPN with an IP from another country, the cart will reflect the country rules of that IP.

Once the customer enters their address, the international confirm page redirects to the confirm page according to the shipping address.

The problem is, when e.g. someone in Germany uses a VPN with an Australian IP, even if the shipping address is Germany, sales tax and shipping fee are not shown on the confirm_germany page or calculated into the sum.

How can this be fixed? I thought maybe the fees should be passed on regardless of the location and then calculated not based on the IP location, but the shipping address. Is that possible?

I'm sure it is possible. You just have to look at the code you are using that calculates the location based on the IP address and override it with the shipping information once it is entered. I could help with that in a premier support ticket.

Thanks, I sent a request for a premier support ticket. Anytime is good, as I work all hours.

I can do it on Monday... Friday is booked. I'll reply to your email.