Adding VAT at checkout

[whitecandle]

Hi

We run a store which has about 1,500 products within the catalogue.

We are shortly introducing VAT @ 20% to all our sales.

I do not want to have to go back into all 1,500 and select VAT from drop down and add TAX to every product. Instead I'd likle the checkout process to add it at the end of the process in one place, is this possible?

We use ver 1.3.x

I've tried a few things, other than having to change every product I'm not sure how this is possible.

Thanks in advance.