Explain double-entry bookkeeping for a first-year accounting student: why every transaction has a debit and a credit, using a small shop buying stock on credit and paying rent in cash, and show the T-accounts.

The shop buys £200 of stock on credit. No cash leaves the shop. So why does the accountant write it down twice? Every transaction has this shape.

A transaction splits into two entries: a debit on the left, and a credit on the right. Both sides must total the same, so the accounting equation stays balanced. Next we'll watch two examples: £200 of stock bought on credit, and £150 of rent paid in cash. Then we read both in their T-accounts.

Here's the rule: every transaction changes at least two accounts, so it gets at least two entries. Debit is simply the left column. Credit is simply the right column. No good, no bad.

A T-account is a table: the account name sits on top, Debit on the left, Credit on the right. Now the shop buys £200 of stock on credit from a supplier. Inventory is an asset, and it has grown, so we put £200 in the Debit column. The shop now owes £200, so in Accounts Payable we put £200 in the Credit column.

Two accounts, two entries — that's double-entry. Now the rent. The shop pays £150 rent in cash. In Rent Expense, £150 goes in the Debit column.

In Cash, £150 goes in the Credit column, because the asset has shrunk, and decreases go on the right. Now compare them with the two from the stock purchase. Add up both sides: total debits £350, total credits £350. They match.

Watch the equation. Assets equal Liabilities plus Equity. Inventory is up £200, cash down £150. Payables are up £200, equity down £150.

Still balanced. Quick tip: don't memorise 'debit means increase'. For cash, a debit increases it and a credit decreases it. Every transaction makes two changes, so debits and credits always match.

Always match. A cash sale. The shop sells goods for £80. Debit Cash £80 — the asset grew.

Credit Sales £80 — income was earned. Now the shop pays its supplier the £200 it owes. Accounts Payable is debited £200 — the debt goes down. Cash is credited £200 — cash goes down.

Two accounts fall, still one debit and one credit. Now £100 moves from the till into the bank. No outsider is involved. Debit Bank £100.

Credit Cash £100. Total assets don't change — cash simply becomes bank. Yet we still make two entries. So a debit doesn't always mean more.

Here is another lens: the accounting equation. Assets equal liabilities plus equity. Use it as a quick check: every transaction must leave the two sides balanced. If they don't balance, something has been missed.

The T-account lens is better for following one account over time, like Cash. A receipt shows what was paid and what was received — two sides of one sale. Here's the whole idea. A transaction always becomes two entries: one debit on the left, one credit on the right.

Add every debit, add every credit, and the totals match. That is why the equation balances. The £200 of stock needed two entries not because cash moved, but because two things changed. Inventory, Accounts Payable, Rent Expense, Cash: those four accounts carried the whole story.