VAT and TAX function

[paul2463]

Hello Guys

this is not for any shopping cart system or any rebuilding or other peoples work it started off as a bit of fun as someone asked how it was done and I cannot for the life in me figure out how to do it.
[code]
to add UK VAT onto a price (presently 17.5%)
$unitPrice = 10.50;
$totalPrice = round(($unitPrice*1.175), 2);
echo $totalprice;
[/code]

does anyone have the faintest idea how you get it to work out how much was paid in tax if you only had $totalprice to work with?
if you take 17.5% off the $totalprice it doesnt work.

any help gratefully recieved

[paul2463]

isnt it typical, no answers come until you ask the world and then it pops into your head
[code]
$totalprice = 28.07;
$vatAmount = round(($totalprice*0.149),2);
$netPrice = $totalprice - $vatAmount;
[/code]