Book-keeping errors are mistakes made at any stage of the recording process, including:

• Entering a wrong amount in the books of original entry
• Posting a transaction to the wrong account
• Failing to apply the double entry principle correctly
• Making arithmetic mistakes when calculating balances
• Wrongly extracting balances to the trial balance

When these errors occur, the account balances will not reflect the actual transactions that took place in the business.

Errors can originate from different stages in the accounting process:

1. Source documents – failing to record the correct amount from invoices or receipts
2. Books of prime entry – omitting items or entering them in the wrong book
3. Ledger postings – posting to wrong accounts or wrong sides
4. Balancing accounts – arithmetic mistakes when adding up or calculating balances
5. Trial balance – extracting balances incorrectly or placing them on the wrong side

Errors are classified into two main categories based on whether they affect the trial balance agreement.

1. Errors That Do NOT Affect Trial Balance Agreement

These errors do not cause the trial balance to disagree because the total debits still equal total credits. There are six types:

Error of Omission

A transaction is not recorded at all in the books. The trial balance still agrees because nothing was entered.

Example: A cash purchase of TZS 345,000 was completely omitted. No entry was made in purchases or cash accounts, so both sides remain equal.

Error of Commission

An entry is made to a wrong account within the same class (e.g., wrong debtor's account instead of the correct one).

Example: A sale of TZS 250,000 to Hawa Mwalimu was posted to Hawa Maalim's account instead. Both are sales ledger customers.

Error of Principle

An entry is made to a wrong class of account (e.g., an expense recorded as an asset, or vice versa).

Example: Shop shelves purchased for TZS 500,000 were debited to purchases instead of furniture and fittings. This affects the statement of financial position but the trial balance still agrees.

Error of Original Entry

The original journal entry contains a wrong amount that is then posted to both accounts.

Example: Wages paid TZS 100,000 was entered and posted as TZS 1,000,000 in both the wages and cash accounts.

Error of Complete Reversal of Entries

The debit and credit entries are made to the wrong accounts and on the wrong sides.

Example: Cash received from a debtor TZS 204,000 was debited to trade receivables (instead of credited) and credited to cash (instead of debited).

Compensating Errors

Two or more independent errors cancel each other out because they affect equal amounts on opposite sides.

Example: Rent expense account is overcast by TZS 45,000, while wages expense account is undercast by TZS 45,000. The errors cancel each other.

2. Errors That DO Affect Trial Balance Agreement

These errors cause the trial balance totals to disagree because the double entry principle is not followed correctly.

Single Entry Made for a Transaction

A debit or credit entry is made without a corresponding opposite entry.

Example: Cash received from a debtor TZS 34,000 was recorded only in the trade receivables account. No entry was made in the cash account.

Use of Different Amounts

Both debit and credit entries are made but with different amounts.

Example: A credit sale of TZS 58,000 was recorded as TZS 58,000 in sales account but TZS 58,800 in trade receivables account.

Double Entry in the Same Side

A transaction is recorded on the same side (debit or credit) in both accounts involved.

Example: Receipt of interest TZS 50,000 was debited to both cash account and interest income account.

Errors in Balancing Ledger Accounts (Casting Errors)

Mistakes made when adding up account columns or calculating balances.

Example: The totals of a trade payables account are TZS 860,000 (credit) and TZS 675,000 (debit), giving a balance of TZS 185,000, but TZS 165,000 was recorded.

Errors in Placing Balances in the Trial Balance

A balance is placed on the wrong side of the trial balance.

Example: A credit balance in the sales account was placed on the debit side of the trial balance.

The following steps help identify errors in the accounting records:

1. Ensure source documents are systematically numbered, arranged, and filed
2. Trace each transaction from source document to journal
3. Vouch each journal entry to the source document
4. Verify every ledger entry with the originating journal entry
5. Trace every journal entry to the ledger accounts
6. Verify balances in the ledger accounts
7. Extract a trial balance to check if totals agree

Situation: The trial balance of Juma's shop showed the following errors:

Understanding the types and sources of book-keeping errors is important for every bookkeeper. Errors that do not affect trial balance agreement are often harder to detect because the trial balance still agrees. Errors that affect trial balance agreement are easier to spot because the totals will not agree. In both cases, the financial statements will be misleading if errors are not corrected.

In Tanzania, small business owners like market vendors in Kariakoo or shopkeepers in Arusha keep records of their daily sales and purchases. If they make errors such as recording personal expenses as business expenses (error of principle) or forgetting to record a sale (error of omission), their profit calculations will be wrong. This affects decisions about how much profit they can take out or reinvest in the business. Knowing how to detect and correct these errors helps business owners maintain accurate records for better financial planning and tax compliance.