06/18/2026
The 15th business day rule is not a safe harbor for 401(k) deposits. It’s the absolute maximum deadline.
If your company can typically deposit employee deferrals 3 days after payroll, that becomes your standard. A future deposit made 10 days after payroll could still be considered late — even if it’s before the 15th business day.
One simple fix: treat 401(k) deposits like payroll taxes. Same day. Every time. No exceptions.
Read the full article to learn what causes late deposits, how they show up in audits, and how to prevent them next year.
Late 401k deposits aren’t complicated. But they are high-risk and highly visible. The good news is they're the easiest audit finding to fix.
