Deposit Rules for 401(k) PlansOne of the most common mistakes made by 401(k) plan sponsors is failure to deposit participant contributions (i.e. 401(k) deferrals/Roth contributions) and loan payments in a timely manner. Having said that, it is worthwhile reviewing the rules and consequences of making late deposits. What are the rules? In general, the Department of Labor (DOL) requires that participant contributions and loan payments be deposited as soon as the amounts can be reasonably segregated from the general assets of the employer. This is because the amounts are considered to become plan assets at this point in time.