While United Airlines is no longer in the business of handing out free ticket vouchers, there are some still out there that can be redeemed for future air travel. If you have one and you want to pass it to a friend or family member, chances are you won't be able to transfer the voucher into their name -- but you may be able to book them a ticket for the next flight they want to take.
View the voucher to look for information on whether or not the voucher is "transferable." If you see the words "non-transferable" on the voucher, this may be an indication that you won't be able to transfer the voucher to someone else; but since you have to make a call to find out, proceed to the next step in either case.
Call United Airlines' Customer Service department at 1-800-UNITED-1 and have the voucher on hand. Ask for an agent who can help you with a ticket voucher purchase. Provide the agent with the name of the traveling party, the voucher number, the departure and arrival cities and any other pertinent information the agent needs to know. Be sure to make it clear that the person receiving the ticket is not the same person on the voucher. Provided you pay for any remaining balance on the ticket, you should be able to book the ticket with the agent.
Take the voucher to a United ticket counter at your local airport, or mail the voucher to the ticket voucher mailing address:
United Airlines Discount Certificates P.O. Box 6046 Dearborn, MI 48121
Keep in mind that if you mail the voucher, it must be received before your ticket will be confirmed and book. As such, it may be easier to take the voucher to a United counter in person.
Since vouchers can take about two weeks to process once they reach the service center, give yourself plenty of time to make sure your reservation is made without a hitch.