Hello
What we’d like to do is exempt certain users from paying taxes and thus make use of this option in each users profile. However, I now learned that this only works if prices are entered without taxes and then added by the shop. In our case, however, all prices are added including taxes, so the store would have to subtract those again. I asked cs-cart about it and they said they’d probably include this functionality in some future version.
Looking for add-ons, I couldn’t find any that do what we need (please correct me if I’m wrong). Again, the entire issue is that we don’t need to add, but subtract, taxes.
So I figured I’d do it myself. It’s simple enough to hook into the relevant places and change the prices. However, since blocks (largely in the sidebar) are cached by default, prices would be displayed based on the settings of the first person who accessed them after clearing the cache - either with, or without, taxes. I understand that I can manually disable caching for these blocks, but am a little apprehensive, largely because of the potential loss of speed.
Is there a best way to move forward? Suggestions? Am I making things too complicated?
Thank you!
Hello,
By default CS-Cart does not support this feature and we advise to make a custom modification which allows to work tax exempt in the mentioned way so if you are interested in it, please do not hesitate to contact us
We are also at your service
Know that I’m too late in posting 
But want to tell you about our development company - Alt-team!
We have been working with CS-Cart since 2010 year, but many of our developers have more than 7 years of CS-Cart development experience.
We like our job and do our best to meet all customers’ demands and provide the client with the best price and high quality.
We are always ready to help you in any CS-Cart question you have. Contact us.
Best regards, Alt-team.