There is an emergency change of plan and I have to cancel a United ticket. Since it's very cheap there is no reason for me to keep its value.
I called UA and they said there will be no refund on any tax. But apparently the fare rule says:
US/ZP/XF - WILL NOT BE
REFUNDED ON NON-REFUNDABLE FARE TICKETS
which means other taxes can be refunded.

Also, I checked the webpage for travel agency where it lists all types of taxes and whether refundable or not.

https://www.united.com/web/en-US/con...cketguide.aspx

Thanks for your attention. I looked up several threads but didn't find any definite answer. This may sound a stupid question here. I've only canceled tickets with an European carrier in which case it refunded a portion of taxes.