Profit belongs to the owners. Revenues increase profits, so they increase captial, and that makes them credits. Expenses decrease profits, so they reduce capital, and that makes them debits. The treatments of expenses is the same as the treatment of assets. Increass in expenses result in debit entries to the appropriate expense accounts. Revenue is treated the same as liabilities. Increases in revenue are credited to the appropriate revenue accounts, while decreases are debited to the same accounts.