5 working days for every retailer in the UK to change their databases, accounting systems and e-commerce websites to reflect a new VAT rate.

We've already had a couple of new customers phone us for help, either with updating their Filemaker Pro databases or Coldfusion websites to reflect the VAT rate change.

If the system has been well designed in the first place, this should be relatively straightforward. But with the VAT rate not having changed since 1991, there is always the chance that a developer has taken a shortcut and hardcoded it somewhere.

The VAT rate should be stored in one global variable that can be simply changed. Hopefully this is in a database field that the system administrator can access - but it may be buried in a preferences or application file in the code somewhere only a developer can find it. Or worse, it may have been hardcoded into calculations all over the place (as we found in one case today).

A few things to be aware of if you are about to embark on the task of changing the VAT rate yourself:

1. If the VAT rate is stored globally, make sure the VAT rate in use at the time has been stored with historical transactions (or at least the VAT charged has been stored) - and that changing the global rate will not affect reporting of existing transactions.
2. If the VAT rate is stored globally and is easy to change, your prices will all change appropriately. But you may decide you don't want this - what about all those £9.99s becoming £9.77 ? In this case you may not want to pass the VAT cut on to your customers. You may be able to get round this issue by doing a global search directly in your database for net prices affected and replace them with net prices multiplied by the appropriate fraction to avoid the gross price changing - a bit complicated, but definitely preferable to changing hundreds of prices by hand.
3. If you are having to change Coldfusion or PHP code, you might just be able to do a search and replace for everywhere the existing rate is mentioned. But remember to search for all the possible variations - 17.5, 0.175, 1.175, 117.5 etc - there are lots of ways to calculate VAT... (oh yeah, and just in case your developer was particularly obtuse, 85.10638297872340425531914893617 - the fraction to work out the net price from a gross price).
4. Before you change anything, BACKUP, BACKUP, BACKUP, and after you've made the changes, TEST, TEST, TEST.
5. Keep a note of the changes you've made, cause you're going to need to change it all back in 13 months time...

If you think you might need a hand with any of this for a Coldfusion or PHP e-commerce website, or a Filemaker Pro database, please get in touch or leave a comment below. It looks like it's going to be a busy weekend for everybody...