Tax Removed after Coupon Applied

Virtuemart 2.6.6, Joomla 2.5.22, AWOPro 2.2.9
When a coupon is used, the tax is removed. Tax shows properly before the coupon is applied. Once a coupon is applied, the tax is no longer there.

Hello,

Can you give more information so I can try and reproduce?

What calculation rules do you have set up?
And the coupon used, anything special about it?
Are you using some type of one page checkout? If so disable it temporarily and test it out with Virtuemart default cart to see if it is something in the one page checkout.