In some instances. Both an S corporation and a partnership are subject to the taxable income limitation when computing the amount of §179 which can be passed through. The entity can only pass through §179 up to the entity’s taxable income.

However, when computing the taxable income of an S corporation, the entity can add wages paid to shareholder/employees to the taxable income/loss [Reg. §1.179-2(c)(3)(ii)].  
When computing the taxable income for a partnership, the entity can add back guaranteed payments paid to partners [Reg. §1.179-2(c)(2)(iv)]. 
Income from interest, dividends, and nonbusiness activities are not part of taxable income for purposes of a §179 pass-through.