Originally Posted by
Reetmafreen
that explains when my wife and I got a $100 voucher each for a baggage issue on an earlier flight and used it towards a PHX-SAN-PHX routing a few years back as the fare was $96 each, I was expecting to pay a few dollars each in taxes as the total fare was showing as $104+ each after taxes, but the ticketing agent said that I was good with just the voucher.
We we ended up getting upgraded to first both ways to boot!

You got lucky because most of the front end ticketing agents do not know the rules and you will end up with paying all the taxes. You can call AA ticketing and they will refund you taxes ... in a form of another AA voucher. You can use several AA vouchers to pay for 1 ticket and still avoid taxes but the agent should know how to do this right.