Tax policy is a lot more complex than simply finding a country with the "lowest tax rate". Multiple rates come into play, for corporate and personal income.
Dubai has zones that are 100% tax free. These zones include one for Internet ventures. As a US citizen it does not matter if you operate in a 100% tax free zone. All income earned, foreign and domestic is subject to US income tax. Failure to pay taxes or report foreign income is tax evasion.
There are ways around this. You could form an IBC in a country such as Panama that has strict privacy in place. But the issue arises that while you could earn money, and save it in Panama, you will have some serious explaining to do if you ever were caught not reporting the income and have a very hard time bringing it to the USA.
With recent political events in the USA the issue of taxes has come up yet again. While as a business owner you want to make sure you do take advantage of lower taxes whenever possible, there is a fine balance between tax avoidance and tax fraud.
My personal view on it is:
1. Taxes are good, they are actually great. If you are paying 1m in taxes, you are surely doing something right.
I apologize for my political rant, but I am weary of entrepreneurs who identify themselves as Republicans because they hate taxes. The truth is as a small business, your tax structure is a lot different than a multinational corporation. Further, just because you are an S Corp, C Corp or LLC, does not mean you are a Corporation as republicans frame it. You want to support those that support keeping jobs in your own country, and tax policy that grows the middle class. The middle class is your consumer base. You might not have Cops and School teachers subscribing to your SAAS product, but when they have money, they spend it, and it trickles up to your small business.
Don't spend too much time trying to figure out where to do business to "Avoid Taxes". Select where you want to do business on the overall cost to do business there, quality of life if you have to live there, and most of all the type of talent and employees you can attract.
I believe Somalia has the lowest taxes. Hardly anybody has any money, and there are no government services. There really isn't much of a Government to speak of.
I would say Hong Kong, 16.5% for corporate tax. It also has one of the fastest broadband in the world.
Singapore is also on the lookout, 17% corporate tax for profits above 300K and ~8% for profits under 300K. Internet speed is also comparable to HK. It also has good friggin awesome fast railway and bus line.
Canada has very low taxes when you consider how much you get in the way of social services.
I hope you are not going to base your business decision solely on that. There are many parts of the world where businesses do not pay "official" taxes but that does not mean they do not have to pay off... Very often, the saying is true: "You get what you pay for". If you have to pay taxes and as a result enjoy, security, legal protection as well as many other business benefits -- consider it a business expense.