The tax is one imposed upon the carrier, in this case SPrint. It is not imposed by the feder governmetn upon the customer-- the frequent flier himself.

Sprint pretends this is a direct tax on the customer by calling it an "Excise charge." It is a tax on the customer by the carrier, not by the government.

It came as a surprise to me. I just signed up for Sprint/NW miles a couple months ago. I looked at their application, and all I saw was a requirement to sign up for their Nickel Nights. Nothing about an extra $5.03 per month. I find this misleading at best, and probably a lot worse. I am pursuing this.