If you’re using the Simple commerce module, there’s nowhere in there to add taxes/shipping. I did do some reading on paypal to see if there was some way to automatically add it on their end- but didn’t spot one. Then again, the paypal docs take me days to wade through sometimes, so that doesn’t mean there isn’t a way to do it.
I think I’d make a request in feature requests for a place to add it to simple commerce. In the short term- I’d say you have two options. Hit the paypal forums and see if there’s a way to add it there. There isn’t that I know of. Second option- if you aren’t using ‘sale price’- you could enter two prices- sale price is without vat, regular price is with it. And then don’t have the item on sale. Which… is not great, as you may not be able to display everything like you want. (Other option would involve some hacking.)
But short answer- on the EE end, there isn’t a separate field for tax and/or shipping in the simple commerce. But I can see where it would make a good FR. Hm- or possibly an extension- though I think you’ll need db changes to get it working, so an extension might not be sufficient.
Make sense?