"For mid-year hires, you do not need to annualize their income or prorate the $145,000 threshold  ... If a participant's prior year FICA wages from the employer sponsoring the plan exceed $145,000 (indexed to 2024), then all catch-up contributions must be made on a Roth basis. It's not split between contributions made before they hit $145,000 in FICA wages and after.... Employers may automatically switch participants to Roth catch-up as long as the participant is given the opportunity to opt out of this deemed election and stop their deferrals when the applicable IRS limit is reached."  MORE >>