Final answer:
The timing of the audit is the element most likely to be agreed upon with the client during the audit planning process, as it involves coordination with the client's schedule.
Step-by-step explanation:
The element of the audit planning process most likely to be agreed upon with the client before implementing the audit strategy is the determination of the timing of the audit. It is essential for both the auditor and the client to agree on when the audit will take place to ensure that all necessary personnel and documents will be available, and to coordinate with the client’s schedule. Strategies such as the methods of statistical sampling or pending legal matters usually fall under the auditor’s discretion, whereas the determination of evidence relates to the auditor’s judgment to provide a sufficient basis for the opinion, but may not be explicitly agreed upon with the client in detail.