Starting in 2026, new rules will alter 401(k) plans, particularly for high-income workers. Contribution limits are increasing, with enhanced catch-up options for older savers. A significant change mandates that individuals earning $150,000 or more must use Roth 401(k) for catch-up contributions, foregoing immediate tax deductions for tax-free growth later. This impacts those whose employers may not offer a Roth option and could increase current tax liabilities for high earners.