Departure tax from Mexico

I Recently bought an eZed on UA from GDL to IAH and the agent at the counter in GDL wanted to charge me some $40 USD. Told him that was included in the ticket but he insisted it wasn't. Days later, back in the US, I went and asked a UA agent about this. She displayed the ticket, and in the tax breakdown there was a DX Tax of $42.60, which appears to be the departure tax the agent in MX was talking about. It was quite a surprise to have the counter agent wanting to charge my CC for this. I did not pay and took a DL flight instead where that tax is deducted out of my paycheck. The bottom line is that such departure tax was part of the eZed ticket. Has anyone had this issue on UA or any other airline when flying from Mexico to the US?

Some stations do require you pay on-site, and it's not necessarily the only tax. When I flew out of PTY, I had to make a separate departure tax payment as well as some of the other taxes (not nearly as much) that came out of my paycheck.

Was that DX tax the only tax you were charged? If not, you may be right about it being a double charge. I would contact United refunds department and ask them to look into it.

I recently flew out of CUN on UA, my airline. I couldn't check in at the kiosk or online, an agent assisting me stated that the tax had not been paid. I had selected payroll deduct when making my listing, so I canceled that and rebooked, paying the departure tax upfront with my credit card. Even that did not help. Finally, after waiting in line, I was able to speak to an agent at the counter and was told I had to pay an additional $21 on top of the departure taxes already collected via EmployeeRes (equivalent of Travelnet). The last time I experienced something like this was upon leaving Tegucigalpa when flying DL in 2013. I spoke to some of my co-workers once back in the office and they stated that unfortunately, paying that additional $20 or so is required, upfront & on top of the already assumed departure taxes at that.

I have never had to pay additional taxes in Mex (or anywhere), but I always print a copy of my ezed or DL tkt that shows the taxes. Paper is always stronger than phone info because it only has the base info.
Last time I had to pay taxes beyond tkt was Dom Rep and that was at least 10 yrs.