📚 OCR Year 9 Accounting: Quick Reference Formula & Theorem Handbook | OCR 九年级会计：公式定理速查手册
This handbook covers the essential formulas and theorems you need for Year 9 OCR Accounting. Each section pairs an English explanation with its Chinese translation, helping you master the fundamentals of the accounting equation, double-entry bookkeeping, financial statements, and key ratios.
本手册涵盖 OCR 九年级会计必需的基础公式与定理。每个小节都提供英文说明与中文对照，帮助你掌握会计等式、复式记账法、财务报表以及关键比率的精髓。
1. The Accounting Equation | 会计基本等式
The most fundamental rule in accounting is the accounting equation: Assets = Liabilities + Owner’s Equity. This must always balance because every asset a business owns is financed either by borrowing (liabilities) or by the owner’s investment (equity).
会计中最基本的规则是会计等式：资产 = 负债 + 所有者权益。该等式必须始终平衡，因为企业拥有的每一项资产要么通过借款（负债）获得资金，要么来自所有者的投入（权益）。
Assets = Liabilities + Owner’s Equity
资产 = 负债 + 所有者权益
2. The Extended Accounting Equation | 扩展会计等式
When we consider revenues and expenses, the equation expands to: Assets = Liabilities + Owner’s Equity + Revenues – Expenses. This shows that earning revenue increases equity, while incurring expenses reduces it.
当考虑收入和费用时，会计等式扩展为：资产 = 负债 + 所有者权益 + 收入 – 费用。这表明赚取收入会增加所有者权益，而费用则会减少所有者权益。
Assets = Liabilities + Owner’s Equity + Revenues – Expenses
资产 = 负债 + 所有者权益 + 收入 – 费用
3. Double-Entry Bookkeeping (Duality Concept) | 复式记账法（双重概念）
Every transaction has two effects on the accounting equation. For each debit, there must be an equal and opposite credit. The rule “Debit the receiver, credit the giver” helps when dealing with personal accounts, but for all accounts total debits must equal total credits.
每笔交易都会对会计等式产生双重影响。每一笔借方记录，必然对应一笔相等的贷方记录。“借给接受方，贷给给予方”的规则在处理个人账户时很有用，但对所有账户而言，总借方金额必须等于总贷方金额。
Assets increase with a debit and decrease with a credit. | 资产增加记借方，减少记贷方。
Liabilities increase with a credit and decrease with a debit. | 负债增加记贷方，减少记借方。
Owner’s equity increases with a credit and decreases with a debit. | 所有者权益增加记贷方，减少记借方。
Revenue is recorded as a credit; expenses as a debit. | 收入记贷方；费用记借方。
4. Trial Balance | 试算平衡表
A trial balance is a list of all ledger account balances at a particular date. It checks the arithmetic accuracy of the double-entry records – total debits must equal total credits. If they don’t, an error has occurred.
试算平衡表是某一特定日期所有分类账账户余额的列表。它用于检验复式记账记录的算术准确性——借方总额必须等于贷方总额。如果不相等，说明出现了错误。
The formula is simply:
其公式很简单：
Total Debits = Total Credits
借方合计 = 贷方合计
5. Income Statement (Profit & Loss) Formula | 利润表（损益表）公式
The income statement shows the performance of a business over a period. Its core formula is: Net Profit = Gross Profit – Expenses, where Gross Profit = Sales Revenue – Cost of Sales.
利润表反映企业一段时期内的经营业绩。其核心公式为：净利润 = 毛利 – 费用，其中毛利 = 销售收入 – 销售成本。
Step by step: | 逐步计算：
Gross Profit = Sales Revenue – Cost of Sales | 毛利 = 销售收入 – 销售成本
Net Profit = Gross Profit – Total Operating Expenses | 净利润 = 毛利 – 经营费用合计
An example: if sales revenue is £50,000 and cost of sales is £30,000, gross profit is £20,000. If expenses are £12,000, net profit is £8,000.
例如：如果销售收入是 50,000 英镑，销售成本是 30,000 英镑，那么毛利就是 20,000 英镑。如果费用是 12,000 英镑，净利润就是 8,000 英镑。
6. Statement of Financial Position (Balance Sheet) Equation | 财务状况表（资产负债表）等式
The balance sheet shows the financial position at a point in time and is a direct reflection of the accounting equation: Assets = Liabilities + Equity. It is divided into non-current assets, current assets, current liabilities, non-current liabilities, and capital.
资产负债表反映某一时点的财务状况，直接体现了会计等式：资产 = 负债 + 权益。它分为非流动资产、流动资产、流动负债、非流动负债以及资本。
The balance sheet must always balance; the total of all assets must equal the total of all liabilities plus capital.
资产负债表必须始终平衡；资产总额必须等于负债与资本之和。
7. Statement of Changes in Equity | 所有者权益变动表
This statement links the income statement and the balance sheet. The formula for closing equity is:
该报表将利润表与资产负债表联系起来。期末所有者权益的计算公式是：
Closing Equity = Opening Equity + Capital Introduced + Net Profit – Drawings
期末权益 = 期初权益 + 追加资本 + 净利润 – 提款
Drawings reduce equity because the owner withdraws resources from the business. Net profit increases equity because it is retained in the business.
提款会减少所有者权益，因为业主从企业提取了资源。净利润则增加所有者权益，因为它留存在企业内。
8. Straight-Line Depreciation | 直线法折旧
Depreciation allocates the cost of a non-current asset over its useful life. The straight-line method charges an equal amount each year. The formula is:
折旧是在资产的使用年限内分摊其成本。直线法每年计提的折旧额相等。其公式是：
Annual Depreciation = (Cost – Residual Value) ÷ Useful Life (years)
年折旧额 = (成本 – 残值) ÷ 使用年限（年）
For example, equipment costing £10,000 with a residual value of £1,000 and a 5-year life would have annual depreciation of (£10,000 – £1,000) ÷ 5 = £1,800.
例如，一项设备成本为 10,000 英镑，残值 1,000 英镑，使用年限 5 年，则每年折旧 = (10,000 – 1,000) ÷ 5 = 1,800 英镑。
9. Inventory Valuation: Lower of Cost and Net Realisable Value (NRV) | 存货计价：成本与可变现净值孰低
Inventory should be valued at the lower of cost and net realisable value. If the selling price less any costs to sell (NRV) falls below cost, the inventory must be written down. This follows the prudence concept.
存货应按成本与可变现净值孰低法计价。如果售价减去销售费用后的可变现净值（NRV）低于成本，存货就应减记。这体现了审慎性概念。
Inventory Value = Lower of (Cost, Net Realisable Value)
存货价值 = (成本与可变现净值) 中的较低者
NRV = Estimated Selling Price – Costs to Complete and Sell.
可变现净值 = 预计售价 – 完工及销售费用。
10. Liquidity Ratios: Current Ratio and Quick Ratio | 流动性比率：流动比率与速动比率
Liquidity ratios measure a business’s ability to pay its short-term debts.
流动性比率衡量企业偿还短期债务的能力。
Current Ratio = Current Assets ÷ Current Liabilities | 流动比率 = 流动资产 ÷ 流动负债
A safe level is usually between 1.5:1 and 2:1, though this varies by industry.
安全水平通常在 1.5:1 到 2:1 之间，但会因行业而异。
Quick Ratio (Acid Test) = (Current Assets – Inventory) ÷ Current Liabilities | 速动比率（酸性测试）= (流动资产 – 存货) ÷ 流动负债
This excludes inventory because it may not be quickly converted to cash. A ratio of 1:1 is often considered acceptable.
这一比率剔除了存货，因为存货可能无法快速变现。通常认为 1:1 的比例是可以接受的。
11. Profitability Ratios: Gross Margin and Net Margin | 获利能力比率：毛利率与净利率
These ratios express profit as a percentage of sales revenue, showing how efficiently a business is operating.
这些比率以百分比的形式反映利润占销售收入的比例，显示企业的经营效率。
Gross Profit Margin = (Gross Profit ÷ Sales Revenue) × 100 | 毛利率 = (毛利 ÷ 销售收入) × 100
Net Profit Margin = (Net Profit ÷ Sales Revenue) × 100 | 净利率 = (净利润 ÷ 销售收入) × 100
A higher margin suggests better control over costs. Compare margins over time or against similar businesses.
较高的利润率通常表明对成本的控制更好。可将利润率与历史数据或同类企业进行比较。
12. Provision for Doubtful Debts | 坏账准备
Businesses often estimate that a percentage of trade receivables may not be collected. The formula for the provision is:
企业通常会估计一定比例的应收账款可能无法收回。坏账准备的公式是：
Provision = Total Trade Receivables × Estimated Bad Debt Percentage
坏账准备 = 应收账款总额 × 预计坏账百分比
The provision is deducted from trade receivables in the balance sheet to show the net realisable value. An increase in provision is charged as an expense in the income statement.
坏账准备在资产负债表中从应收账款中扣除，以反映可变现净值。坏账准备的增加额将作为利润表中的费用确认。
This ensures that profits are not overstated and assets are not overvalued, following the prudence concept.
这确保了利润不会被虚增，资产不会被高估，符合审慎性概念。
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