Business Guides 6 practical business guides — worked examples, real numbers, and a calculator to run your own. ← All guidesFinanceHealthMathEverydayConstructionElectricalConversionOtherGaming All business guides GST and Reverse Charge Invoices: What Must Be on the PageAug 24, 2026 · 8 min readUS Invoice Rules: Sales Tax and the New 1099 ThresholdAug 21, 2026 · 6 min readROI vs Annualized Return: Why a 60% Gain Can Be MediocreJul 31, 2026 · 5 min readWhy 20% Then 10% Off Is Not 30% OffJul 30, 2026 · 5 min readHow to Calculate Your Break-Even PointJul 21, 2026 · 4 min readMargin vs Markup: The Confusion That Quietly Kills ProfitJul 11, 2026 · 4 min read Browse the business calculators →