Tax Law
Income tax
Know the structure: taxable income, deductions, credits, and the distinction between capital and income. Understand the taxation of individuals (progressive brackets), companies (corporate tax), and the rules on dividends, capital gains, and real estate (betterment tax and purchase tax). Trap: the "substance over form" principle lets the tax authority recharacterize transactions; a label does not control.
International taxation
Know residence vs. source, the foreign-resident exemption, transfer pricing, and controlled foreign corporation rules.
Procedure
Understand assessments, appeals to the tax authority and the courts, and the burden of proof (generally on the taxpayer to show the assessment is wrong).
Worked rule of thumb
For any tax question: (1) what is the taxable event; (2) who is the taxpayer; (3) what is the rate and base; (4) any exemption or treaty; (5) what is the procedural posture?