Most 401(k) plan problems do not start in a conference room.
They start in payroll.
The payroll department controls much of the information that determines whether the plan operates correctly. Compensation, deferral elections, eligibility dates, bonuses, overtime, commissions, ownership information, and contribution amounts all flow through payroll.
One bad code can create a mess.
I have seen plans where certain bonuses were improperly excluded from deferrals. Employees became eligible but were never added to payroll. Deferral percentage changes were not implemented. Loan repayments were missed. Employees received contributions based on the wrong compensation.
Sometimes those mistakes continue for months or even years.
Plan sponsors often assume payroll is simply an administrative function. For retirement plans, it is much more than that. Payroll is one of the most important compliance systems the sponsor has.
The problem is that payroll employees are not always given the plan document or trained on the plan’s rules. They may know how to run payroll perfectly while having no idea which compensation is included under the 401(k) plan or when a new employee becomes eligible.
That disconnect can become expensive.
Corrections may require additional employer contributions, lost earnings, participant notices, amended filings, and professional fees. What looked like a small payroll mistake can become a significant compliance project.
Plan sponsors should regularly compare payroll practices against the plan document. Compensation codes should be reviewed. Eligibility procedures should be tested. Deferral changes should be monitored. Someone should verify that contributions are transmitted correctly and on time.
Your payroll department does not need to become an ERISA law firm.
But it does need to understand the rules it is responsible for administering.
Because when payroll breaks, the 401(k) plan usually breaks with it.