Does anyone know if you can pay for departure tax by credit card or do you have to have pesos. I have seen many different amounts. Does it have to be paid at the airport?

It is normally included in your ticket price.

I do not recall ever having to pay a departure tax in Mexico. I have paid in other countries such as Domonican Republic but not Mexico. As mentioned above, it might be hidden...

It used to be a separate item you had to pay at your departure airport, quite awhile ago.

But, at least for me, and for many years now, it's been part of the ticket price.

Yes Suze back in the "Olden Days" it had to be the exact amount as they did not make change & it had to be in Pesos. Then for a while they took US Currency then perhaps 15 years or so ago they started including it in the cost of the ticket.
I remember well but of course you are much too young to recall.

The only people who have to pay a separate departure tax are UK citizens flying a charter such as Thomas Cook or Thomsens, all others it is included in the ticket price.

Thanks for the clarification. I contacted Southwest Airlines as well & they confirmed that it was included in the ticket. Just a couple of years ago we had to pay a departure tax when we left Costa Rica so nice to know that we don't have to.