In double-entry bookkeeping, a debit signifies a decrease in which items?

Introduction / Context:
Understanding how debits and credits affect different types of accounts is fundamental in double entry bookkeeping. Many students memorise that debits are good or bad without grasping that the effect depends on the nature of the account. This question asks specifically where a debit entry indicates a decrease, focusing on revenues, liabilities and owner's equity. Knowing these relationships is essential for recording transactions correctly and interpreting financial statements.

Given Data / Assumptions:
- The system in use is double entry bookkeeping. - The question asks where a debit signifies a decrease. - The accounts listed are revenues, liabilities and owner's equity. - We assume standard classification of accounts into assets, liabilities, equity, income and expenses.

Concept / Approach:
In double entry, every account has a normal balance side. Asset and expense accounts normally have debit balances; debit entries increase them and credit entries decrease them. Liability, equity and revenue accounts normally have credit balances; credit entries increase them and debit entries decrease them. Therefore, when we post a debit to a revenue account, it reduces revenue. A debit to a liability account reduces the amount owed. A debit to an owner's equity or capital account reduces the owner's claim on the business. All three of the categories listed in the options normally carry credit balances, so a debit entry signifies a decrease in each of them.

Step-by-Step Solution:
Step 1: Recall the normal balance rule: debit increases assets and expenses, credit increases liabilities, equity and revenues. Step 2: Recognise that liabilities, revenues and owner's equity are all accounts that usually have credit balances. Step 3: Conclude that to decrease such credit balance accounts, we must post a debit entry. Step 4: Since a debit decreases all three categories mentioned, the correct answer is the combined option that states all of the above.

Verification / Alternative Check:
Consider examples. When a business pays off part of a loan, the loan payable account (a liability) is debited to reduce it. When sales returns occur, the sales revenue is reduced via a debit to a returns account that contra credits revenue. When the owner withdraws funds, drawings are debited, which reduces owner's equity. In each case a debit entry reduces a liability, revenue or equity balance, confirming the pattern described.

Why Other Options Are Wrong:
Revenues only: While a debit does reduce revenues, this option ignores the similar effect on liabilities and owner's equity. Liabilities only: A debit reduces liabilities, but the option is incomplete because owner's equity and revenues are also decreased by debits. Owner's equity only: Again, this is incomplete, as both liabilities and revenues share the same credit nature and are decreased by debits.

Common Pitfalls:
Students sometimes incorrectly think of debit as always meaning increase or always meaning decrease. A more reliable approach is to link debit and credit to the normal balance of each account category. Remembering a simple table, where debit increases assets and expenses and credit increases liabilities, equity and revenue, helps avoid confusion. From that table, it is easy to deduce that a debit must reduce liabilities, equity and revenues.

Final Answer:
The correct option is All of the above, because a debit entry decreases revenue accounts, liability accounts and owner's equity accounts, all of which normally carry credit balances in double entry bookkeeping.