VAT goes up from 17.5% to 20% today (4 Jan 2011). If you are running a MySQL database with prices in it then this may be useful. My tables had prices in them that already included VAT at 17.5%, so to update to the new rate I ran two queries. First set the price back to non-VAT.
UPDATE stock SET price = price / 1.175
And then run the prices through the maths to update to the new rate of 20%.
UPDATE stock SET price = price * 1.2
A lovely New Year’s present from good old Nick Clegg and David Cameron.