Lesson 2 of 6 · 3 min
The two-sided rule
Here’s the one idea that makes accounting different from a checkbook: money never appears from nowhere. If your cash goes up by $500, something has to explain it - you earned it, borrowed it, or put it in yourself.
just means you write down both sides of every transaction: where the money came from, and where it went. The two sides are always equal, so the books can’t quietly drift - if they don’t match, you know something’s missing.
Debit and credit are just “left” and “right”
A is the left side of an entry, a is the right. They are not “good” and “bad,” and a debit isn’t always an increase - it depends on the account. The only rule that always holds: in every entry, the debits and the credits add up to the same number.
- Got paid $500. Checking goes up (debit $500), Sales goes up (credit $500).
- Bought $42 of supplies with the card. Supplies expense goes up (debit $42), the credit card balance goes up (credit $42).
- Paid $200 toward the card. The card balance goes down (debit $200), Checking goes down (credit $200).
In day-to-day use you rarely type “debit” or “credit.” You describe what happened in plain words and Parline records both sides. This is just so the app makes sense when you look under the hood.