I have a small business and I have not filed a tax return for the past 3 years because the business operated at a loss. Do I have to file anyway? Does it matter if the business is a sole proprietorship or a corporation? I have not been contacted by the IRS regarding no tax returns (so far)

File, even if there is no immediate benefit, because you may be able to carry forward your losses to offset future profits and thus reduce taxes.

Technically you were supposed to file anyway... not saying very many small struggling new businesses do. Keep those records!

What is the nature of this business? Is it a side business you run out of your home as a sole proprietorship? Or do you have an office or store? It does not matter whether it is a corp or sole proprietorship as to whether you file or not, you should file anyway. But if it is a side business you could be taking your losses against other income.