Tax witholding

-- url of the page with the problem -- : www.portal-gestao.com/
-- HikaShop version -- : 262
-- Joomla version -- : 351
-- PHP version -- : 5.5.31
-- Error-message(debug-mod must be tuned on) -- : No error

Hello,

For some products, the customer is obliged to retain 25% of the net value (before any other taxes, like VAT), if it is a company.

So, a product with a gross price o €100, for example, would cost to a company:
100 - 25 (tax witholding) + 23 (VAT) = €98
And to a private customer:
100 +23 (VAT) =€123

How can I configure this in Hikashop?

Thank you.

That's it,
Thank you so much!