When must proof of service be filed if a party does not waive or accept service?

The requirement to file proof of service no later than the time the served party must respond is essential to ensure that the court is aware that proper legal procedures have been followed. This timing guarantees that the court can verify that the served party has indeed been given notice of the legal action and has adequate time to prepare their response.

In legal proceedings, service of process is a crucial step, as it communicates to the defendant that they are being sued, thus providing them with an opportunity to respond. Setting the deadline for proof of service to align with the time frame in which the served party must respond helps maintain the fairness and integrity of the judicial process.

This timing requirement is particularly important because it prevents any ambiguity about whether the defendant has been properly notified. If proof of service were to be filed after the response deadline, it could create confusion regarding the defendant's requirement to respond and potentially impact the case's timeline or the court's ability to enforce responses and decisions.

The correct choice captures the essential procedural emphasis on clear communication and maintaining a fair legal process for all parties involved.