Originally Posted by
SWAVictor
Also, vouchers can not be used to pay taxes and fees, so you will need to use CC, gift card, or travel funds to cover those.
The workaround is to buy a slightly more expensive ticket (to anywhere), cancel and refund the taxes to your card, then use the travel credit to buy the trip you want. For example, suppose your trip costs $120 plus $20 tax. Find another trip that costs $140 plus tax. Use the voucher and credit card to book that. Cancel immediately and refund the taxes. Use the $140 travel credit to buy your $120 plus $20 tax trip.
Most people won't bother with this, but it's available if you need it.