Nundina › Discover calendars › Retirement Contribution Deadlines calendar › 💼 401(k) Employee Contribution Deadline (Tax Year 2027)💼 401(k) Employee Contribution Deadline (Tax Year 2027)31 December 2027Last day to make employee elective-deferral contributions to a calendar-year 401(k) for tax year 2027. Verified via IRS guidance, 2026-07.Retirement Contribution Deadlines calendarMore from this calendar