Don't know if this will help but there is a VRT calculator on the Revenue website (www.revenue.ie) which might be of assistance. There are lots of variables, like where the vehicle is coming from, commercial or private, age, mileage and so on.
cheers Mark, seem like anything unusual that you throw at them yields a 'no result found'. guess if you want to import anything other than a punto they'll pick a number for you to pay on the day.
You can also phone them up on the number given on the web site, they give you an estimate which is close enough to the figure they calculate on the day, depends on spec and condition, how the assessor is feeling at the time etc.
I think Rosslare is the head office. A couple of my queries have been referred on to Rosslare by the South County Dublin office, so I think if you call them directly you might be eliminating the middleman.
