{"slug":"what-is-a-special-memorandum-account","qid":"sma_ledger","label":"One margin account through four events: equity, requirement, and SMA","post_title":"What Is a Special Memorandum Account (SMA)?","post_url":"/blog/what-is-a-special-memorandum-account#q-sma_ledger","columns":["event","market_value","debit_balance","equity","reg_t_requirement","margin_excess","sma","buying_power"],"rows":[{"event":"Start","market_value":40000,"debit_balance":20000,"equity":20000,"reg_t_requirement":20000,"margin_excess":0,"sma":0,"buying_power":0},{"event":"Deposit 5k cash","market_value":40000,"debit_balance":15000,"equity":25000,"reg_t_requirement":20000,"margin_excess":5000,"sma":5000,"buying_power":10000},{"event":"Stock gains 8k","market_value":48000,"debit_balance":15000,"equity":33000,"reg_t_requirement":24000,"margin_excess":9000,"sma":9000,"buying_power":18000},{"event":"Stock gives 8k back","market_value":40000,"debit_balance":15000,"equity":25000,"reg_t_requirement":20000,"margin_excess":5000,"sma":9000,"buying_power":18000},{"event":"Buy 12k on margin","market_value":52000,"debit_balance":27000,"equity":25000,"reg_t_requirement":26000,"margin_excess":-1000,"sma":3000,"buying_power":6000}],"shape":"table","sql":"WITH ledger AS (\n    SELECT 1 AS step, 'Start' AS event, 40000 AS market_value, 20000 AS debit_balance, 0 AS sma_entry\n    UNION ALL\n    SELECT 2, 'Deposit 5k cash', 40000, 15000, 5000\n    UNION ALL\n    SELECT 3, 'Stock gains 8k', 48000, 15000, 4000\n    UNION ALL\n    SELECT 4, 'Stock gives 8k back', 40000, 15000, 0\n    UNION ALL\n    SELECT 5, 'Buy 12k on margin', 52000, 27000, -6000\n)\nSELECT\n    event,\n    market_value,\n    debit_balance,\n    market_value - debit_balance                        AS equity,\n    0.50 * market_value                                 AS reg_t_requirement,\n    market_value - debit_balance - 0.50 * market_value  AS margin_excess,\n    SUM(sma_entry) OVER (ORDER BY step)                 AS sma,\n    2 * SUM(sma_entry) OVER (ORDER BY step)             AS buying_power\nFROM ledger\nORDER BY step","computed_at":"2026-08-19T15:20:56.717937+00:00","elapsed":0.002585765}