A Value Added Tax (VAT) number used by businesses to collect VAT (a type of sales tax). The number is issued to businesses by Her Majesty's Revenue and Customs (HMRC) in the United Kingdom. You'll need a sales tax number if you are a business and want to claim back VAT paid for goods and services purchased. Without a valid sales tax number, you may not be able to get back the VAT you've paid.
Ask the business for a VAT invoice. If the company is registered for VAT, it must give you a VAT invoice if it sells you taxable goods or services.
Look on the invoice for the VAT number. While an invoice must show the VAT number, there is no requirement about where on the invoice the number must be located. A VAT invoice must show a wealth of information so check carefully to make sure you haven't missed the number.
Check any VAT number with the Taxation and Customs Union via the VAT number validation website. If you suspect that you have been given an invalid VAT number (and you are the owner of a VAT number yourself), you can use this system to validate a VAT number.
If the business won't give you an invoice, you should decline the purchase and report the business to HMRC. A business who refuses to give you a VAT number may be subject to a fine.