On a brand new van you will need to get it ex VAT because you will be liable for VAT here too on the invoice price plus any shipping costs.
To show the absolute swindle that VRT is, it's calculated as 13.3% of the VAT and VRT inclusive price on a new MoHo. To illustrate this, say your landed cost is €50k, you then add 23% vat bringing you to €61,500. It's not simply a case of compounding another 13.3% here because the 13.3% is based on the total tax inclusive figure X where
€61,500 + 13.3%X = X
So €61,500 = X - 0.133X = 0.867X
Then X = €61,500/0.867 = €70,934.26
So finally you can calculate the VRT as 13% of €70,934.26 which is €8,015.57
You can simplify this as compounding at a rate of 13.3% ÷ (100% - 13%) = 15.34% but the powers that be want to keep it needlessly complicated and pretend the rates are that little bit lower than they effectively are. No prizes for guessing the minister for finance who introduced VRT, the most cunning and devious of them all