Introduction
Bookkeeping in debits and credits is more than five centuries old: the library of the Institute of Chartered Accountants in England and Wales holds what it describes as the earliest known printed book about double-entry book-keeping, Luca Pacioli's Summa de arithmetica of 1494. Company ledgers still record transactions that way. Yet investment bankers almost never write a journal entry. They answer the same underlying question in a different language: what does this transaction do to the income statement, the cash flow statement and the balance sheet?
That is a deliberate choice, not a gap. Statement effects show what a client, an investor or a model actually sees across the three financial statements, while debits and credits describe how a ledger is kept. The vocabulary still surfaces in audit adjustments, diligence reports and conversations with a target's finance team, so a small amount of it is worth knowing.
The Only Rules Worth Memorizing
Double-entry bookkeeping records every transaction in at least two accounts, with total debits equal to total credits. That single constraint is why the accounting equation always holds: whatever is added on one side of the balance sheet is matched by an equal change somewhere else.
- Journal entry
The record of a single transaction in the books, listing each account affected and whether it is debited or credited. Total debits must equal total credits in every entry.
Which side increases an account depends only on the account type, and the pattern mirrors the accounting equation. Assets sit on the left of the equation and grow with debits, the left-hand side of an entry; liabilities and equity sit on the right and grow with credits. Revenue and expenses are the only rows that need a second thought.
| Account type | Increased by | Decreased by | Normal balance |
|---|---|---|---|
| Assets | Debit | Credit | Debit |
| Expenses and dividends | Debit | Credit | Debit |
| Liabilities | Credit | Debit | Credit |
| Shareholders' equity | Credit | Debit | Credit |
| Revenue | Credit | Debit | Credit |
Revenue and expenses follow the equity pattern because they end up in retained earnings: revenue raises equity, so it behaves like a credit, while expenses reduce it and behave like debits.
Three more terms complete the working vocabulary. The general ledger holds every account and its running balance; a T-account is the classroom sketch of one account, debits on the left and credits on the right; and the trial balance lists every account's closing balance to prove total debits equal total credits. The financial statements are assembled from the trial balance, which is why a target's controller may send one in diligence, and why the first job with it is mapping each account to the statement line it feeds.
Translating a Journal Entry Into Statement Effects
Take a $10 increase in depreciation. The bookkeeper's entry is short: debit depreciation expense by $10, credit accumulated depreciation (the running total that reduces property, plant and equipment, or PP&E, on the balance sheet) by $10. A banker describes the same event across the statements, and immediately adds what the entry alone leaves out:
- Income statement: pre-tax income falls by $10; at a 25% tax rate, taxes fall by $2.50 and net income by $7.50.
- Cash flow statement: net income is down $7.50, the $10 non-cash charge is added back, and cash ends up $2.50 higher.
- Balance sheet: net PP&E is down $10, cash is up $2.50, and retained earnings are down $7.50, so it still balances.
The journal entry records the pre-tax expense and the lower net PP&E, nothing more. The tax saving is booked in a separate tax entry, and the add-back is not an entry at all: it only appears when the cash flow statement is prepared from the other two statements. That gap is exactly why bankers reason in statement effects: they force every consequence onto the page. The full method, applied to any transaction, is laid out in tracing a transaction through the statements.
When the Vocabulary Matters for a Banker
Debits and credits reappear in a few places on a deal. Audit adjustments are proposed as entries ("debit deferred revenue, credit revenue"), and a quality of earnings report may pick up the adjustments a target's auditor proposed but the company never recorded. Purchase accounting schedules in an acquisition can be built as entries too. Reading them only requires the table above and a habit of asking which statement line each account belongs to.
Candidates coming from audit face the reverse problem: they think in entries and need to learn to speak in statement effects, on top of the modeling and valuation skills that moving from Big 4 accounting into banking requires.
For everything else in this guide, statement effects are the working language. Debits and credits remain the bookkeeper's notation: worth recognizing when a schedule uses them, and worth translating into income statement, cash flow and balance sheet effects before drawing any conclusion from them.
