Every Story Has Two Sides
Double-entry bookkeeping is the mechanical discipline that keeps the accounting equation true after every event. Its rule: every transaction is recorded as at least two entries — a debit and a credit of equal amount — so the books always balance.
The vocabulary is counter-intuitive, so learn it mechanically first, understand later:
| Account type | Debit (left) | Credit (right) |
|---|---|---|
| Asset | Increase | Decrease |
| Expense | Increase | Decrease |
| Liability | Decrease | Increase |
| Equity | Decrease | Increase |
| Revenue | Decrease | Increase |
The mnemonic pattern: assets and expenses (left-side family) grow with debits; liabilities, equity, and revenue (right-side family) grow with credits. Debit and credit are not synonyms for good and bad — they are column labels: left and right.
A T-account is the visual tool: draw a T, write the account name on top, debits on the left limb, credits on the right. The balance is the difference: an asset account typically sits debit-heavy (more increases than decreases), a liability account credit-heavy.
The duality principle is the link to the equation: debits increase the left side (assets) and decrease the right side (liabilities, equity), while credits do the reverse. Because each entry has equal debits and credits, the equation is preserved automatically — double entry is the accounting equation in operating form.
Example: pay a 200 supplier invoice.
- Debit: Accounts Payable 200 (liability decreases — debit a right-side account).
- Credit: Cash 200 (asset decreases — credit a left-side account).
Both sides of the equation fall by 200. The entry is self-checking: if you only record one side, the trial balance screams.
Tip: The pattern is one sentence: the left-side family (assets, expenses) grows with debits; the right-side family (liabilities, equity, revenue) grows with credits. Everything else is that sentence applied.
Common pitfall: Importing everyday meanings — "debit bad, credit good." In bookkeeping they are pure directions, left and right. A debit to Cash is money arriving; your bank statement's vocabulary is written from the bank's perspective, not yours.