What type of transaction allows clients to track job costs without affecting financial statements?

The correct choice is a zero dollar expense. This type of transaction is specifically designed for tracking job costs without impacting the overall financial statements. A zero dollar expense allows you to record costs associated with a particular job or project, enabling detailed tracking and analysis of expenses incurred, while not affecting the profit and loss accounts since it does not involve an actual cash transaction or a flow of funds.

Utilizing a zero dollar expense is particularly useful for organizations that want to keep thorough records of expenditures that need to be monitored for budgeting or project management purposes. These entries can help provide insights into job costing and project profitability without the complications that arise when actual expenses are recorded, which would directly affect financial reporting.

In contrast, the other options focus on transactions that do involve monetary implications or impact financial statements. For instance, billable time reflects actual services rendered and impacts income when billed, while a zero dollar invoice serves as a formal request for payment without an actual cash transaction, which can also affect accounts receivable processes. A credit memo typically reduces revenue or accounts receivable, thus affecting financial outcomes.