According to UK VAT legislation you need to fill and submit the given form to Amazon. When you buy qualifying goods and services, you'll have to give the seller a written declaration that you are entitled to buy these goods without VAT. This declaration has to give enough information to show that you qualify. If you can't sign the written declaration yourself, the signature of your parent, guardian, doctor or another responsible person is acceptable on the declaration.
To know more about this VAT eligibility please go through the following link :
http://www.hmrc.gov.uk/vat/sectors/consumers/disabled.htm
You can send this form in a PDF format or as a scanned copy to the following email address :
vat-refund-requests@amazon.co.uk
Once we've received this information, we will proceed with processing your claim and issue you with the appropriate VAT refund.