the fairtax organization has proposed a "prebate" to mitigate regressiveness.

https://fairtax.org/about/how-fairtax-works-slideshow

They've proposed that, but as far as I can tell it's less of a serious proposal and more an instance of an "overcoming objections" sales tactic. I don't see how a flat sales tax can achieve revenue-neutrality (itself a major selling point of FairTax) while also offering a large enough "prebate" to avoid being enormously regressive in practice. Considering the misleading nature of a bunch of other FairTax claims [1], I pretty much consider distrust to be the only tenable default position with respect to anything else they say.

[1] http://www.factcheck.org/2007/05/unspinning-the-fairtax/

That seems like a reasonable effort. Thanks.