The accounting equation is the foundation of all financial reporting. It states that:
Assets = Liabilities + Equity
Every transaction a business records must keep this equation in balance. If assets increase, either liabilities or equity must also increase, or another asset must decrease by the same amount. This self-balancing property is what makes double-entry bookkeeping work and is the reason the balance sheet always balances.
The three components
Assets
Assets are resources owned or controlled by the business that are expected to provide future economic benefit. They are split into two categories on the balance sheet:
| Category | Examples | Typical timeframe |
|---|---|---|
| Non-current (fixed) assets | Property, plant, equipment, vehicles, intangible assets | Held for more than 12 months |
| Current assets | Cash, bank balances, trade debtors, inventory, prepayments | Expected to be used or converted to cash within 12 months |
Liabilities
Liabilities are obligations the business owes to external parties. Like assets, they are classified by timeframe:
| Category | Examples | Typical timeframe |
|---|---|---|
| Current liabilities | Trade creditors, VAT payable, PAYE due, bank overdraft, accruals | Due within 12 months |
| Non-current liabilities | Bank loans, mortgages, finance lease obligations, deferred tax | Due after more than 12 months |
Equity
Equity (also called shareholders’ funds or net assets) represents the residual interest in the business after all liabilities have been deducted from all assets. It comprises:
- Share capital – the nominal value of shares issued
- Share premium – amounts paid above nominal value
- Retained earnings – accumulated profits not distributed as dividends
- Other reserves – revaluation reserves, hedging reserves and similar items
For a sole trader, equity is simply the owner’s capital account plus accumulated profits less drawings.
Why the equation always balances
The equation balances because every transaction has two effects. This is the core principle of double-entry bookkeeping. There is no transaction that can affect only one side of the equation.
Consider a company that receives a £20,000 bank loan:
- Assets increase: cash in the bank goes up by £20,000
- Liabilities increase: the loan obligation goes up by £20,000
Both sides of the equation increase by the same amount. The equation remains in balance.
Now consider a company that pays £5,000 to a supplier:
- Assets decrease: cash goes down by £5,000
- Liabilities decrease: trade creditors go down by £5,000
Again, both sides decrease by the same amount. Balance is maintained.
How common transactions affect the equation
| Transaction | Assets | Liabilities | Equity | Balance maintained? |
|---|---|---|---|---|
| Owner invests £50,000 cash | +£50,000 | – | +£50,000 | Yes |
| Buy equipment for £10,000 cash | Equipment +£10,000, Cash -£10,000 | – | – | Yes |
| Buy inventory on credit £3,000 | +£3,000 | +£3,000 | – | Yes |
| Receive payment from customer £2,000 | Cash +£2,000, Debtors -£2,000 | – | – | Yes |
| Pay supplier £3,000 | -£3,000 | -£3,000 | – | Yes |
| Earn revenue £8,000 (cash) | +£8,000 | – | +£8,000 (profit) | Yes |
| Incur expense £1,500 (cash) | -£1,500 | – | -£1,500 (profit) | Yes |
| Declare dividend £2,000 | – | +£2,000 | -£2,000 | Yes |
| Pay dividend £2,000 | -£2,000 | -£2,000 | – | Yes |
Notice that some transactions affect only the asset side (one asset increases, another decreases). Others affect assets and liabilities. Revenue and expenses flow through to equity via retained earnings.
The expanded accounting equation
The basic equation can be expanded to show how revenue and expenses affect equity:
Assets = Liabilities + Share Capital + Retained Earnings + (Revenue - Expenses)
Revenue increases equity (through profit), while expenses decrease it. At the end of each accounting period, the net profit or loss is closed off to retained earnings, returning the equation to its standard three-part form.
This expanded form makes it clearer why the income statement and balance sheet are interconnected. The profit or loss reported on the income statement flows directly into the equity section of the balance sheet.
The equation and the balance sheet
The balance sheet is simply the accounting equation presented in a structured format. Under UK company law and FRS 102, the balance sheet can be presented in two formats:
Format 1 (vertical)
| £ | |
|---|---|
| Non-current assets | 150,000 |
| Current assets | 80,000 |
| Total assets | 230,000 |
| Current liabilities | (45,000) |
| Non-current liabilities | (60,000) |
| Total liabilities | (105,000) |
| Net assets | 125,000 |
| Share capital | 50,000 |
| Retained earnings | 75,000 |
| Total equity | 125,000 |
Net assets (£125,000) equals total equity (£125,000). The equation holds.
Format 2 (net current assets)
Many UK companies present the balance sheet showing net current assets (current assets less current liabilities) as an intermediate subtotal. The result is the same – total equity equals net assets.
Using the equation to check your books
The accounting equation provides a powerful error-detection mechanism. If the equation does not balance, there is an error somewhere in the books. Common causes include:
- A transaction recorded with unequal debits and credits
- A transaction recorded in only one account
- An arithmetical error in a ledger balance
- A misclassification between asset, liability and equity accounts
Running a trial balance (a list of all account balances) is the standard way to check whether debits equal credits and, by extension, whether the accounting equation is in balance.
Limitations of the equation
The accounting equation is infallible as a mathematical identity, but it has practical limitations:
- It does not tell you which account contains an error, only that one exists
- Compensating errors (two equal and opposite mistakes) will not cause an imbalance
- Errors of principle (posting to the wrong type of account) may not disturb the balance
- The equation works with book values, which may differ significantly from market values
These limitations are why double-entry bookkeeping is supplemented by reconciliations, analytical review and audit procedures to identify errors that the equation alone cannot catch.
The equation and UK financial reporting
Under the Companies Act 2006 and FRS 102, every UK limited company must prepare a balance sheet that demonstrates the accounting equation. Directors are required to confirm that the accounts give a true and fair view, and the balance sheet is one of the primary financial statements used to satisfy this requirement.
For unincorporated businesses, HMRC expects financial records to be maintained on a double-entry basis (except for the smallest businesses using the cash basis). The accounting equation underpins the reliability of these records and the tax returns derived from them.