Double-Entry Accounting System for Small Business

2025-02-22

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Русская версия

This guide outlines a robust yet lean double-entry accounting system that scales with your business. Our goal is accuracy and clarity through a well-structured chart of accounts, transaction logs with strict invariants, and separate planning tools.

1. Chart of Accounts

The chart of accounts is your financial roadmap. Each account has a unique code and role:

• Assets: What you own (e.g., cash, inventory).
• Liabilities: What you owe (e.g., accounts payable, accrued expenses).
• Equity: Owner contributions and retained earnings.
• Revenue: Income from sales or services.
• Expenses: Costs incurred (e.g., customs duties, spoilage, mobile expenses).

Account Code Structure

Account codes are organized in ranges that reflect their type:

• 1000-1999: Assets (cash, inventory, receivables)
• 2000-2999: Liabilities (payables, loans)
• 3000-3999: Equity (partner contributions, retained earnings)
• 4000-4999: Revenue (sales, exchange gains)
• 5000-5999: Expenses (customs duties, spoilage, mobile)

Each code's first digit indicates the account type, making financial statements easier to prepare and analyze.

Sample Chart:

2. Transaction Log & Invariants

Every transaction consists of multiple entries that must adhere to three key invariants:

• Balance Invariant: Each transaction must include at least one debit and one credit entry that sum to equal amounts.
• Completeness Invariant: All required fields (date, transaction ID, account code, amount, etc.) must be completed.
• Single-Source Invariant: Each entry should appear only once per transaction; no duplicates or omissions.

Core Transaction Log Example

Imagine a simple cash injection by Partner A. This transaction demonstrates all invariants.

Invariant Checks:

• Balance: Total debits (2,000) equal total credits (2,000).
• Completeness: All fields are filled with clear notes.
• Single-Source: Transaction TX001 uniquely ties both entries to the same event.

3. Specific Transaction Examples

3.1 Recording Initial Balances

Scenario: Starting accounting with 15,000 Pesos already in the cash register.

Notes:

• Use transaction ID "TX000" to indicate this is the opening entry
• Opening Balance Equity account tracks pre-existing assets/liabilities
• Future owner contributions should use Partner Contribution accounts instead

3.2 Foreign Currency Safe Deposit

Scenario: Deposit $100 into a USD safe at 20 Pesos/USD; later withdraw at 22 Pesos/USD.

Deposit (2025-02-01):

Withdrawal (2025-02-10):

3.2 Three-Way Transaction: Mixed Funding

Scenario: Purchase inventory for 6,000 Pesos. Corporate cash (Account 101: Cash Domestic) only has 4,000 Pesos. The remaining 2,000 Pesos is contributed by Founder A.

Journal Entry (2025-03-15):

Invariant Checks:

• Balance: Total debits (6,000) equal total credits (4,000 + 2,000).
• Completeness & Single-Source: All fields are complete; TX600 uniquely identifies this combined event.

3.3 Multi-Month Payment Plan for Recurring Expenses

Scenario: A business has a contract for mobile service and must pay monthly. Each month, the company records the expense and the liability, then clears the payable when the payment is made.

Month 1 – Provider A (500 Pesos)

Month 2 – Provider B (600 Pesos)

3.4 Accounts Payable for Materials

Scenario: The business receives materials on credit (5,000 Pesos) and pays a month later.

Receipt (2025-02-05)

Payment (2025-02-25)

3.5 Inventory Spoilage

Scenario: The business purchases inventory worth 10,000 Pesos and later finds that 15% of it (1,500 Pesos) is spoiled. The value of inventory is adjusted accordingly.

Purchase (2025-02-03)

Spoilage (2025-02-20)

Notes:

• The spoilage expense reflects a reduction in usable inventory.
• The business still records the full original purchase, with an additional expense entry for the loss.

4. Lost Transaction Examples

Lost transactions violate the single-source invariant, meaning an entry is either missing or duplicated, causing inconsistencies in the transaction log.

4.1. Missing Credit Entry

This scenario shows a partner deposit where only the debit side is recorded, breaking the balance.

• Issue: The corresponding credit entry to "Partner A Contribution" is missing.
• Fix: Add the missing credit entry.

4.2: Duplicate Entry

This example shows a supplier payment recorded twice, which incorrectly inflates the total cash spent.

• Issue: The payment was recorded twice.
• Fix: Remove the duplicate entry to ensure cash outflow matches the actual transaction.

4.3: Missing Receipt Discovery

This example shows how unrecorded transactions can lead to cash discrepancies that are later resolved.

Initial Cash Count (2025-03-20)

Expected cash balance is 10,000 Pesos, but physical count shows only 8,700 Pesos.

Receipt Found (2025-03-22)

Later, a misplaced receipt for office supplies is discovered.

• Issue: Physical cash count revealed missing money, initially recorded as loss.
• Resolution: Finding the receipt explained most of the shortage, leaving only 300 Pesos as true unknown loss.
• Learning: Implement same-day receipt processing to prevent similar issues.

5. Pivot Tables & Budget Planning

• Pivot Tables:
  Use pivot tables to aggregate transaction data. Build trial balances, income statements, and balance sheets by filtering account types. Pivot tables also help flag invariant violations when totals do not zero out.

• Budget/Forecast Tab:
  This planning layer is separate from the transaction log. Use it to project future expenses and revenues (e.g., recurring mobile fees, expected import costs). Formulas can auto-populate recurring items, but the budget never affects historical transactions.

5.1 Example Budget for the Next Three Months

Notes:

• The budget is separate from the transaction log and is used for planning only.
• Actual expenses in the transaction log will be compared against the budget to track variances.
• Adjustments can be made monthly based on revenue fluctuations.

6. Automated Checks in Google Sheets

These formulas help catch errors early by automatically validating transactions as they're entered.

6.1 Account Code Validation

Use Data Validation to ensure only valid account codes are entered:

1. If using a formal Google Sheets table: reference the column directly with =Table[Column]
2. If using regular ranges: create a named range AccountCodes from the codes in your Chart of Accounts
3. In transaction log, select Account Code column
4. Data → Data Validation → List from range → Use either =AccountCodes or =ChartTable.Code

Formula to flag invalid codes: =IF(COUNTIF(AccountCodes, B2)=0, "Invalid Code", "")

6.2 Account Name Lookup

Automatically display account names based on codes: =IF(B2="", "", VLOOKUP(B2, ChartOfAccounts, 2, FALSE)) Where:

• B2 is the Account Code cell
• ChartOfAccounts is a named range including codes and names
• 2 refers to the column containing account names

6.3 Transaction Balance Check

For each Transaction ID, verify debits equal credits: =IF(SUMIFS(DebitColumn, TransactionIDColumn, D2) = SUMIFS(CreditColumn, TransactionIDColumn, D2), "Balanced", "ERROR")

Add conditional formatting to highlight unbalanced transactions:

1. Select the entire transaction row
2. Format → Conditional formatting → Add rule
3. Format rules:
   • Apply to range: Select all columns in your transaction log
   • Format cells if... Custom formula is:

   =SUMIFS($DebitColumn, $TransactionIDColumn, $D2) <> SUMIFS($CreditColumn, $TransactionIDColumn, $D2)

   • Formatting style:
     • Red background: #F4CCCC
     • Red text: #990000
     • Bold text
4. This will highlight the entire row for any transaction where debits don't equal credits

6.4 Completeness Check

Flag missing required fields: =IF(OR(ISBLANK(A2), ISBLANK(B2), ISBLANK(C2)), "Missing Data", "")

6.5 Running Balance Check

For cash accounts, maintain running balance: =SUMIFS(DebitColumn, AccountCodeColumn, "1001") - SUMIFS(CreditColumn, AccountCodeColumn, "1001")

Add conditional formatting to highlight negative balances.

Conclusion

The transaction log must always adhere to balance, completeness, and single-source invariants. Errors such as lost transactions (missing entries) and duplicate transactions can cause major inconsistencies and must be corrected immediately.

The Budget Tab serves as a separate planning tool and never interferes with actual recorded transactions. It allows businesses to forecast future expenses and compare actual performance against expectations.

By maintaining these structures properly, a small business can ensure clear, accurate, and scalable bookkeeping.