Corporate tax and income tax share the same statutory framework under the IRC but apply to fundamentally different taxpayers. Specifically, corporate income tax applies exclusively to C-corporations as independent legal persons filing Form 1120, taxed at the flat 21% federal rate. Income tax encompasses individual, fiduciary, estate, and corporate taxation as a broader legal category. Consequently, the 21% corporate income tax rate operates on an entirely separate computational track from the 10%–37% individual income tax brackets that apply to pass-through business income flowing to shareholders on Schedule K-1. Furthermore, understanding this distinction prevents costly structural errors — particularly for business owners deciding between C-corporation and pass-through operation, where the effective combined tax rate differential can exceed 10 percentage points depending on distribution policies and individual bracket positioning.