So I setup a virtuemart 3.8.6 / AwoCoupon 3.6.0.7 and cannot produce the issue with the info you have given me.
I setup:
- calculation rule, tax bill 5%
- 1000 euro product
- ten, 10% discount coupon
- in awocoupon set calculation type to discount after tax
And this is my cart:
If I set it up as 'discount before tax'
Both cases are correct. In your last example, you showed Virtuemart coupon. Virtuemart only does discount before tax. For AwoCoupon, did you update the configuration to use discount before tax? Do you have a checkout extension, can you temporarily disable it and test? Do you have any plugins in vmcoupon section that are enabled other than AwoCoupon? If so, try disabling temporarily and testing.