Validate VAT numbers from the desktop

If you run a business (or look after the books for one), sometimes it can be useful to be able to double check VAT registration numbers to ensure they are valid, or to simply look them up to find an address. Double checking a UK VAT number can be done with some simple maths1, but all that does is ensure it could be a valid number, not that it is one. Better, then, is to be able to punch the number into an online service, and be told not only that it is valid, but who it belongs to.

Prior to the end of the Brexit transition period, I often did this using the European Commission’s VIES VAT number validation service, but now that the UK is fully outside of the EU, that service is no longer available. Other such services do exist, however, such as the one on – but while that service works just fine in NetSurf, it is only able to look up the numbers for UK-registered businesses.

Solving this particular Brexit-related problem for RISC OS users, Kevin Wells has released a new application called VATGST. This makes use of Curl to pass the VAT number to the application programmer interface (API) provided by VAT Sense, which is able to look up both UK and EU numbers, and return registration details.

As well as VAT numbers, though, VAT Sense – and therefore VATGST – goes one step further; the clue is in the name of Kevin’s application; it can also look up registration numbers for Goods and Service Tax (GST – sometimes also referred to as a General Sales Tax). This is a type of sales tax that is used in some countries and is in many ways similar to Value Added Tax (VAT) used here in the UK and in the EU.

Unfortunately, the VAT Sense service uses a subscription model based on the number of requests made per month, with a free level of up to 100 requests. This means that if Kevin released the software with a registered API key at that level, any given user might find it doesn’t work if 100 requests had already been made that month by others. Therefore, and to keep the software free, he has instead released it so that the user must register with VAT Sense for their own API key.

When it is first run, it will ask for this, so you’ll need to visit the VAT Sense website to register. For most people, this will probably be the free 100 requests per month, but other options include £4.99 per month for up to 500 requests, going all the way up to £99.99 per month for up to 50,000 – though I doubt any RISC OS users will need that many!

If you find any of Kevin’s software useful, don’t forget to check out his merchandise shop or simply shout him a coffee.


  1. UK VAT registration numbers should be nine digits long. Multiply the first digit by eight and write down the result, then multiply the second digit by seven and write down the result… and continue doing this until you’ve multiplied the seventh digit by two and written down the result. The next step is to add up all of the results you’ve written down. From the total, deduct 97, and keep deducting 97 until you have a negative number. That negative number should be the same as the last two digits of the VAT registration number. I imagine there will be techniques employed for registration numbers for other countries – but that’s the one for the UK.

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