The non-preferred CO Chase MC Debit card did not earn miles for me, but the preferred version of the card reportedly worked for Ikar (message 78) and a card from another bank worked for DCBob (post 64). To get the $3.89 flat price from payusatax, as Ikar explained in post 63, you have to click "continue" instead of "debit card". Anyhow, the user interface has "back" buttons, so you should be able to try other answers if you are not seeing the $3.89 flat price.

If you still have trouble getting the $3.89 flat price on payusatax, please feel free to send me a private message and I will try to help. I made screen snapshots of most of my steps, which I can refer to, but many have my private information in them.

It would be interesting to learn what results you get and exactly which kind of Citi debit card you use (I assume it earns some kind of rewards, right?).