So it has no rules on what portion of SS income is really "taxable income" ?
SS income isn't taxed under the Flat Tax.
when to consider investment income, stock options or bonds as "taxable income" depending on who issued them, when purchased and when sold ?
Investment income isn't taxed under the Flat Tax.
there is nothing a business needs to keep track of in terms of capitalized vs. depreciated costs so that "taxable income" can be figured ?
There is no depreciation under the Flat Tax. Capital expenditures are written off. A business would pay tax (the same rate as individuals) on total revenue from sales of goods and services less purchases of inputs from other firms less wages, salaries, and pensions paid to workers less purchases of plant and equipment.
what about not-for-profit businesses ?
They would be exempt from the business tax but would have to pay tax on any fringe benefits they give their employees.
is welfare income ?
It doesn't matter, the Flat Tax doesn't tax income on the personal side – it only taxes wages, salaries, and pensions.
how about food stamps or housing assistance ?
Those aren't wages, salaries, and pensions so they aren't taxed.
if you sell your home, are there rules about how much of any gains are "taxable income" ?
None.
do they depend on marital status ?
There is no marriage penalty with the Flat Tax.
what if you were married and divorced several times while you held the house ?
Why would that matter?
what about rental income, depreciation, gains on selling, etc. ?
Rental income would be considered business income.
