You already know the fundamental accounting equation: Assets = Liabilities + Equity. This is the bedrock of the balance sheet. But to understand the day-to-day operations of a business, we need to expand it. Equity isn't just a static number; it's constantly changed by the company's activities.

Specifically, equity increases with revenues and decreases with expenses and owner withdrawals (or dividends). So, we can expand the equation to show these moving parts.

This formula is the engine of double-entry accounting. Every single transaction a business makes can be described as a change within this equation. The key is that it must always remain in balance. For every action, there is an equal and opposite reaction somewhere in the equation.

To keep the equation balanced, accountants use a system of debits and credits. Forget any preconceived notions you have about these words. In accounting, "debit" simply means the left side of an account, and "credit" means the right side. That's it.

Whether a debit or a credit increases or decreases an account's balance depends on the type of account it is. This is where the expanded equation is crucial. Accounts on the left side of the equation (Assets) increase with debits. Accounts on the right side (Liabilities, Equity, Revenue) increase with credits. Expenses are the exception: they reduce equity, so they increase with debits.

A common mnemonic to remember this is DEAD CLIC.

• DEAD: Debits increase Expenses, Assets, and Drawings.
• CLIC: Credits increase Liabilities, Income (Revenue), and Capital (Equity).

Every transaction will have debit entries and credit entries, and the total value of the debits must always equal the total value of the credits. This ensures the accounting equation remains balanced.

The first place a transaction is recorded is in the general journal. This is a chronological log of all business activities. Each entry, called a journal entry, shows the date, the accounts affected, and the debit and credit amounts. Let's look at a couple of complex examples that show the system's power.

Example 1: Deferred Revenue

A client pays your company $6,000 on December 1st for a six-month service contract. You have the cash, but you haven't earned it yet. You have an obligation to perform the service.

This creates a liability called Unearned Revenue. Here's the initial journal entry:

Cash (an asset) increases with a debit. Unearned Revenue (a liability) increases with a credit. The equation is balanced.

Now, at the end of the month on December 31st, you've completed one month of service. You've now earned $1,000 of that revenue ($6,000 / 6 months). You need an adjusting entry to recognize this.

Here, we decrease the Unearned Revenue liability with a debit and increase Service Revenue with a credit. This accurately reflects that the company has earned one month's worth of the fee.

Example 2: Accrued Expenses

Your company's two-week pay period ends on January 5th, but your fiscal year ends on December 31st. As of Dec 31st, your employees have worked for one week and earned wages, but they haven't been paid yet. Let's say they've earned $5,000.

Even though no cash has been paid, the company has incurred an expense and has a liability to pay its employees. This is an accrued expense and must be recorded.

Wages Expense increases with a debit, and the liability Wages Payable increases with a credit. When the employees are actually paid on January 5th, the entry will involve debiting Wages Payable (to reduce the liability) and crediting Cash.

After transactions are recorded in the general journal, the next step is to post them to the General Ledger (GL). The General Ledger is a collection of all the individual accounts for a company, like Cash, Accounts Payable, Service Revenue, etc. Posting is the process of transferring the debits and credits from the journal to their respective accounts in the ledger.

Think of each account in the GL as a T-shaped diagram. The left side is for debits, and the right is for credits. When we post our first transaction (receiving $6,000 cash), we would add $6,000 to the debit side of the Cash T-account and $6,000 to the credit side of the Unearned Revenue T-account.

At the end of an accounting period (like a month or a year), we calculate the final balance for each account. The last step is to prepare an unadjusted trial balance. This is simply a list of all the accounts in the general ledger and their final debit or credit balances. The primary purpose is to verify that the total of all debit balances equals the total of all credit balances.

If the totals match, it's a good sign that the posting process was done correctly. It doesn't guarantee there are no errors, but it confirms the fundamental equation is in balance.

Notice that Unearned Revenue has a $5,000 balance ($6,000 credit - $1,000 debit). Our debits equal our credits, so the books are in balance. From here, accountants can proceed to create the financial statements.

Time to test your understanding of these mechanics.

Mastering this cycle of journalizing, posting, and balancing is the core skill of bookkeeping. It ensures financial records are logical, orderly, and always in equilibrium.