Help with Taxes

[wovendesign]

Hi im new to this and am requesting some help regarding the taxes for zones.

I have a UK tax set up fine and its working on the system adding 15% ontop of the product and the shipping but now I need to add a different version for rest of the world (not including USA and canada as this will be set up at a later date).

Now I have set-up a tax rate that will only work with ROW address in zone and its working but the setup I have is -15% as its exempt from VAT. So for example on a £19.95 purchase (inc shipping) its giving me the cost of £18.45 when im checking out when it should be £16.96.

Why isnt it taking 15% off of the total including shipping? am I missing something as I said im a newbie so be gentle. (ive also attached a snapshot of the detail too if that helps?)

[wovendesign]

sorry should have mentioned the version of zen-cart I have etc...

Zen Cart 1.3.8a
Database Patch Level: 1.3.8

Hope someone can offer some advice...