You should complete this declaration if you are 'chronically sick or disabled' and the goods or services are for your own personal or domestic use. A family member or carer can complete this on your behalf if you wish.
You can find out more from the Helpsheets on the GOV.UK website or by telephoning the VAT Disabled Reliefs Helpline on Telephone: 0300 123 1073. HMRC staff cannot advise whether or not an individual is chronically sick or disabled.
A person is ‘chronically sick or disabled’ if he or she is a person:
It does not include an elderly person who is not disabled or chronically sick or any person who is only temporarily disabled or incapacitated, such as with a broken limb.
For more information on VAT exemption please read this.