Income

It’s payday. Your checking account goes up by 8,192 USD. You open your ledger, add one line — salary came in, cash went up — and move on with your day. That entry feels complete. It balances, the number matches the deposit, nothing is wrong. And yet you’ve just thrown away most of the information you were actually paid. Because 8,192 USD isn’t your income. It’s what’s left of your income after the government, your retirement account, and your health plan have each taken a slice. Your real paycheck was 16,667 USD. The gap between those two numbers — everything that happened on the way from gross to net — is where nearly all the interesting financial information lives. If the only thing you record is the number that lands in your account, you’ve deleted it. This is the single most common mistake I see people make when they start keeping their own books. It’s worth understanding exactly what you lose, and how little effort it takes to keep it. ...