Checkout change w/wo tax

Hi,

If taxes are removed after the login, it probably means that the billing or shipping address of the customer is in a zone not covered by the tax rules you configured in the System>Taxes menu.
So for example, if you have there only one tax rule with the zone "France" selected, if the address of the customer is not in France, then the tax rule won't apply to him, and thus he will see the prices without taxes after logging in.

So to do what you want depends on how you want taxes to be based on the location of the customer, what are the location allowed, etc. To come back to my example, you could simply remove the zone in your tax rule and thus the tax rule would apply regardless of the zone of the address. But maybe that's not what you want ? It depends on what you're selling and to who you're selling it and your local tax rules.