This guide covers business taxation from entity selection through examination and collection. It begins with self-employment tax and the estimated payment system, the two features that produce nearly every first-year failure. A full part compares how each entity form is actually taxed, including the reasonable compensation question that drives most S corporation examinations and the basis rules that limit loss deductions. Separate parts address payroll obligations and the trust fund recovery penalty that attaches personally and permanently, the deduction rules and the categories that generate disputes, depreciation and expensing choices, and accounting method as the principal timing tool available to a small business. Further parts cover recordkeeping standards that decide examinations, how a business audit proceeds, deficiency and collection procedure, worker classification from the tax side, state and local obligations including nexus, and retirement plans as the largest remaining deduction. Authority is cited and linked throughout.