Which type of contribution must be made to comply with a traditional ADP safe harbor?

To comply with a traditional Actual Deferral Percentage (ADP) safe harbor, the contributions made must meet specific requirements to ensure that the plan is nondiscriminatory. The correct response describes the necessary contribution structure: specifically, that contributions must be at least 100% of the first 3% of employee elective deferrals. This means if an employee defers 3% of their salary into the 401(k), the employer is required to match this with a contribution equal to 3%.

This structure is designed to encourage participation and help balance the benefits provided to highly compensated employees with those received by non-highly compensated employees. By establishing this minimum contribution requirement, the plan is considered to comply with safe harbor provisions, allowing it to avoid certain testing requirements during plan compliance testing. Therefore, this option correctly identifies the standard for contributions under a traditional ADP safe harbor plan.

The other options either do not meet the safe harbor requirements or mischaracterize the necessary contribution structure, making them unsuitable for ensuring compliance with ADP safe harbor provisions.