Taxation in various countries differs considerably, and requires
a quite different structure for the calculation. For technical
reasons, Kartris has this value set in the
web.config rather than in the config settings,
meaning it is not changeable from the back end of
Kartris.
This value gets set during the setup
routine, and it's unlikely most stores would ever need to change this.
But if for any reason you do, you can find the tag in the
web.config file and change it
manually.
The tax system in Kartris works differently for US/simple models, and EU tax.
The tax rates page itself is only really active when the tax regime is set to EU. It will list various rates which can be used for the various bands of VAT in your country. For example, in the UK these would be 0%, 20%, 5%, etc.
Once these are set, you can choose which tax band applies when creating or editing product versions. For example, in the UK some items such as childrens' clothes are exempt from VAT, while most items will come under the 20% tax band.