A flexible expense is an expense that occurs on a regular schedule, but the amount allotted toward the expense can be adjusted, such as a utility bill. Expenses are typically categorized into three categories: fixed, flexible and discretionary expenses.
Fixed expenses are expenses that occur regularly and stay constant from one month to the next. Discretionary expenses are expenses that are not on a regular schedule and are completely voluntary, such as entertainment or dining expenses. Discretionary expenses are sometimes categorized as flexible expenses. Emergency expenses are expenses that are very infrequent and cannot be planned for, such as a car needing repairs.