i ran into the problem of my section 179 being limited. why? because turbotax does not enter / calculate your eligible business income. it only calculates Sked F and Sked C at Line 3a. plus some other items. in my case, i had very little positive income from F and C. F had a big loss and C had a gain so it was pretty much a wash.
section 179 is limited to actual "business income" where you materially participate. so if you have net biz losses, you can't take any 179.
in my case the key was line 3b, where i could manually enter my rental real estate income. that is because i classify myself a real estate professional who actively participates in my rental properties. once i manually entered this at 3b, my limitation went away. furthermore, my calif. state tax dropped dramatically too. so this is an extremely important oversight on the part of turbotax software. turbotax should automatically include Sked E income (for r. e. professionals) at this page which is called "Depreciation Options" in your list of forms. which carries over to Form 4592 "Section 179 Summary". took me forever to figure this out, especially in view of all the other arcane deprecation rules such as the new Special Depreciation Allowance. further note on the latter: if you elect SDA instead of 179, then you are forced by irs regs to use SDA for all of that class of property across your return. i didn't want to do that. so i went back to using 179, where you can elect to deduct all of an item in year 1. which amounts to the same result, as far as i can tell.
