I'm a believer in uniformity and have long favored a flat tax and elimination of the capital gains and inheritance taxes by folding both into the income tax.
I'd begin that uniformity with the definition of income which I would classify as any money a person (or couple) receives minus any costs they paid to secure that income. That's it. It wouldn't matter if the money comes from work, capital gain on investment, capital gain on sale of property, the lottery, welfare checks, inheritance, gambling, found money, etc. Expenses would be anything from steel toe shoes, cost of commuting to work, cost of the stock or other property for which there was a gain, dry cleaning, etc. To eliminate much of the headache of tax filing I'd keep a standard deduction to account for basic expenses a person pays that goes with having a job instead of accounting for most of this crap.
That uniformity I like also includes making the corporate tax rate the same as the personal tax rate which would be the same rate for head of households, singles, couples filing jointly, couples filing individually, and couples that anybody is outraged at why the government classifies them as couples.
Naturally the broader we include what is income the simpler the tax code, the less tax avoidance games people need to play, and the lower the fixed tax rate can be set.
