I have a client that owns an S corp and funds a SIMPLE IRA with us.

When is the deadline for him to deposit his final 2022 employee salary deferral? My understanding is that employee contributions are due within 30 days of the month in which the deferred payments were made, so his December 2022 (final 2022 SIMPLE IRA employee contribution) contribution could be deposited in his SIMPLE IRA up until the end of January. Is that correct?