If there were even a small flat tax that was levied on all levels of the population, from rich to poor, that would probably bring in more money to governmental agencies than is brought in now. At this point the loopholes and tax shelters for the rich mean they are not even paying that much.
It's a viable source of revenue and a (relatively speaking) fair way to apply taxation in this country, I see no real in-depth arguments against it. There are some that say it's bad but few if any that propose an alternative that is better, if it was such a flawed system we'd have people able to suggest a better one.
Yes, a flat tax is a viable source of revenue for governmental agencies, because people will pay higher taxes when their businesses are more profitable. Flat tax systems still tax people, but they also leave an incentive to earn the next dollar. Governments will end up raising more revenue by using the flat tax.
A national sales tax, especially in America, is a fair tax for everyone and here's why. If you make more money, you generally spend more money. Hence, the rich pay more in taxes than the poor on a cumulative basis! The tax rate stays the same, but if someone buys a house for $1 million, the sales taxes paid are cumulative more than someone who buys a $100,000 house. It just makes sense. Add in excise taxes on things such as cigarettes, alcohol, gasoline and marijuana and there should be plenty of tax revenue for everyone. We live in a consumer-based society, so taxes should be based on spending money as opposed to making money.
I believe a flat tax is a far more viable source of revenue for a government, especially in comparison to the United States current tax tiers. I believe it would be far easier for the government to know ahead of time, how much money they could expect to collect and then divide those resources in a more concise way.
What makes it complicated are all the write-offs and exceptions, not the mere fact that it is tiered. That's easy, you calculate X% for one range of money, Y% for another range, Z% for another. It's NOT hard.
What makes taxes hard are all the exceptions and write-offs. We could simplify the tax system not by having a flat tax but by having progressive tiers without any deviations allowed from that system for any reason.