They want a Value Added Tax.
The VAT is a real killer. It taxes at every level of the goods from manufacturing to the end sale. A one dollar item becomes two dollars by the time it is sold.
A national Retail Tax is taxed at its final sale. A One Dollar Item is sold for $1.15 at the final sale if the tax is 15%, or whatever the rate is.
A VAT is a tax at EVERY LEVEL.... it is a sales tax + a tax on every step... this is why socialists love it