Antonyms for the term "source income" include terms such as "expense," "deduction," and "liability." While source income refers to the stream of revenue that an individual or business generates, the aforementioned terms represent the opposite end of the financial spectrum. Expenses refer to the amount of money that a company or individual must pay out in order to sustain operations or maintain a certain standard of living. Deductions, on the other hand, refer to any reduction in taxable income, such as investments, childcare costs, or mortgage interest payments. Liabilities are any debts or financial obligations that an individual or business must pay, which can be a result of loans, credit card purchases, or other financial transactions.