Hello Alexm,
Okay, This unfortunately is NOT a straightforward process in Prestashop (apparently they don't like tax exemptions). There's ALSO an add-on, but it's not free, here's the link:
Manage Tax Exempt customers
The process I came up with depends on creating a new TAX based on a LOCATION. The nice thing about PrestaShop is that you can easily add new locations. And you can name them for that very purpose. Prestashop creates taxes per STATE and you can you also create a TAX RULE that will apply to a range of zip codes so that you can cover multiple locations. You would need to change the address of every member of your group to the new State that you created. Then if they were to checkout, the tax would be 0. Note that if this member were ever to LEAVE that group, you would need to change the address in order to make sure that the tax exemption was removed.
Here's a step summary:
1) Login to the Prestashop Administrator Dashboard
2) Create a New State and assign 0% tax. The name of the state you create should be something that reflects what you're trying to do so that you can find it and understand it without having to look through its settings. For example: TX-Groupname-TaxExempt.
3)Adjust the addresses for your Group users so that they have the same location state or country.
4) Save the change.
The users assigned to that state will now only have 0% tax when checking out. Note that his applies tax based on CUSTOMER location.
Of course this is a LOT easier if you decide to purchase the module, but as you can see, the module solution that Prestashop provides is not free.
If you have any further questions, please contact technical support or leave a comment at the bottom of the page.
Regards,
Arnel C.