It’s simple. You, or the person you care for, needs to receive the Higher Rate Mobility Component of Disability Living Allowance. You also qualify if you get the Enhanced Rate Mobility Component of Personal Independence Payment, the War Pensioners’ Mobility Supplement or Armed Forces Independent Payment. You can see if you’re eligible here.
If you still need to apply for your mobility allowance, or you want a copy of your award notice that details your entitlement, just contact the Department of Work and Pensions.