Which option best describes the payment method for contracted commissary items?

The best description of the payment method for contracted commissary items is payroll deduction because this method allows for the costs of items purchased to be deducted directly from an employee's paycheck. This process is efficient and convenient for both the employee and the contracting agency, ensuring timely payment for commissary goods without the need for immediate cash or credit transactions.

In the context of managed incidents, such as wildland firefighting, payroll deduction simplifies the logistics of payment by reducing the need for employees to carry cash or engage in more complex transactions like credit purchases. It also allows for easier tracking of expenses related to commissary items.

The other methods would not be as fitting. Immediate cash payment may cause delays or complications, especially if an employee does not have cash readily available. A credit transaction would imply using a credit card or some form of credit line, which may not always be practical in a field situation. Direct invoicing would typically be more complex and may create additional administrative burdens, making it less desirable in the fast-paced environment of incident response where efficiency is crucial.