A pretty massive difference especially considering that latter is still annymous from the consumers standpoint. Retailer are already audited up the ying-yang now. The reporting and complaince mechanisms for collecting sales tax are already in place.
Of course on all transactions, and on all of its details. If you are the government, you aren't just going to collect the tax. The *new* IRS will record the price before the tax, the price after the tax, the date, the location, the item, the seller, the buyer, etc. etc.
What is just another field on a government spreadsheet?
Another thing that just makes me laugh about this 'fair tax' drivel is that supporters think that the IRS will go away. There is ALWAYS an administrative agency to collect and record taxes.
Under your system, the IRS *might* disappear. But a STIC (Sales Tax Information Commission) will appear. Believe it!!