Alright, after reading the bill (both the actual bill FairTax Bill a simple english summary) I have a few more insights that bear talking about.
The main arguments currently against the FairTax in this thread are:
1) Tax evasion will be rampant.
2) The FairTax will become as convoluted as the current Tax code.
3) Price increases on imported goods by adding the FairTax.
4) A person can simply import goods from another country.
5) Administering the Prebate will be expense and will form a new agency.
6) People will simply barter their goods to avoid the tax.
1) You say that people will evade the FairTax, and you are right. However, it is of note that there will be a reporting system via telephone or other means to report violations of FairTax Law (Section 501(d)). There will also be a rewards program for people who "assist ... in discovering or prosecuting tax fraud may be remunerated" (Section 501(h)). This will help in keeping down the evasion rate. I understand that this will not eliminate tax evasion, but it will help cap it. This is not the only anti-evasion measure. Another measure will be that every business shall designate a tax matters person (Section 502). I must assume that this person will have some say in the business dealings. If the tax matters person is found out to be lying, then he, along with the perpetrator, will be prosecuted for tax avoidance, which can be punishable by upto 2 years in prison (Section 505). That person will not risk his own interests for that.
2) The FairTax rate is determined the sum of the General Revenue rate, the Social Security rate, the Medicare rate (Section 101). The rate can be adjusted, but only by adjusting these three rates. HR-25 calls for a General Revenue rate set at 14.91, a Social Security rate at 6.31, and the Medicare rate at 1.78 (Section 904, for a combined Federal Tax Rate of 23%. The revenue raised by the FairTax is allocated proportionately between the three rates, as determined by the each rate's proportion to the total Federal Tax Rate (Section 904) (eg. General Revenue @ 14.91 gets 64.83% of FairTax revenue, etc.)
3) Section 905 lays the groundwork for adjusting the the FairTax rate within Treaties between foreign governments. The FairTax rate applied to imported goods produced outside of the US Tax system can and most likely will be adjusted to a more favorable rate. We do this mutually with the other country. This will put American goods on a much better competitive footing internationally. Exported goods have no tax bill, either embedded or applied (Section 102 and 203). This will help revive more jobs in manufacturing and production.
4) When imported goods (going directly to an end user) go through customs they must have a declared value, which will be taxed. The purchaser is responsible for paying the FairTax (Section 101). Since these goods have not been under any US Tax before this, all goods, whether new or used, will be taxed under the FairTax. The FairTax defines a used item as one that has not been taxed either under US Income laws or under the FairTax (HR-25 Page 17 line 12). So all imports that are not for business use will be taxed.
5) The Prebate will be administered by the Social Security Administration in the form of checks in the mail, electronic funds transfer to a bank account, or a "smart card" which can be used much like a bank debit card (Section 304).
6) People that barter goods are responsible to pay the FairTax on the item priced at current market values (Section 103(f)). If they fail to pay they will be penalized for failure to comply just as they would if they did not remit the FairTax to the STA of their state. Consequently if two people barter goods, they both get things of equal value to them with no loss of profit, therefore IMHO no tax should be assessed. If two businesses do it, it is an business to business transaction and is already FairTax free.
Any more questions that I can do my best to answer? I will add them to new lists to answer from HR-25 itself, with commentary provided by myself.