I think you should add a tick box in the VAT config so that the store owner can define whether their prices already include VAT or not. If the box is not ticked (and the prices are therefore assumed to be excluding VAT) then whatever the VAT rate is should be added to all prices for products and shipping for customers in the cart totals, or if the box is ticked, then the store owner defines their pricing including VAT, and the cart then subtracts the VAT to provide the breakdown in the cart summary. I think this can be done as an update to the existing UK VAT module, with the tick-box selected by default (assuming the prices include VAT), so that an update of the module would not affect any existing installations, but by not ticking the box, then store owners can define their pricing excluding VAT.
hello, you can do it by using "The VAT inclusive prices as defined in the product details are intended for" option
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