under the present system a max of half of social security income can be taxed and it is taxed at your marginal rate, in my case 10% for a max tax on my expected social security payments of about $950. under the fair tax system assuming i spend my social security payments the full amount would be taxed at approximately 23% for a total tax of about $4000 on social security payments alone.
as i said, they will have to fix this or it won't fly.
NO income is taxed under the FairTax until (and if and when) you spend it on taxable things ... and not everything is taxed. You need to inform yourself more thoroughly on how the FairTax operates. And recognize also that you receive a prebate each month (which also is not taxed until, etc. spent).