Every accounting period (monthly, quarterly), your CFO needs an income statement: a summary of revenue, costs, and profit over the period. The good news: it's literally a SQL query over your journal lines, grouped by account type, filtered by posting date. The bad news: most fintechs have a chart of accounts that's grown organically, with revenue scattered across 40 accounts and expenses across 80. This lesson uses a tightly-curated CoA to show how a clean income statement falls out of well-named accounts. We post one revenue + one COGS + one opex entry so the structure is visible.