Which action must be taken if an employee wishes to change their contribution amount in a qualified retirement plan?

To change their contribution amount in a qualified retirement plan, an employee must contact the plan administrator. The plan administrator manages the day-to-day operations of the retirement plan and is responsible for maintaining records of contributions, investments, and benefits. By reaching out to the plan administrator, the employee ensures that their request to alter their contribution is processed correctly and documented in accordance with the plan's specific procedures.

Other actions, such as submitting a written request or informing a supervisor, might be part of the internal processes within some companies, but they do not fulfill the requirement to formally update the contribution amount. The plan administrator has the authority to make the necessary adjustments to the retirement plan settings, which is why direct communication with them is essential.