The purpose of a blank taxi cab receipt is to provide proof of the trip. Many types of clients will request receipts. Those who need receipts for tax purposes or travel expenses are at the top of the list. Many professionals such as lawyers, doctors or others who bill clients for travel use receipts for expenses. People who often travel between locations such as freelance writers, photographers, salespersons, contractors and visiting home health professionals use receipts for tax purposes to claim deductions.