For 2023, the allowed max salary deferral for a 403b or 401k plan is $22,500 (or $30,000 if age 50 by the end of the year). If you have already funded an amount to an employer sponsored retirement plan via salary deferral, then you will be limited in your allowed salary deferral at a second place of employment in a year, whether you work a second job or change jobs throughout the year.
If you do overfund your allowed salary deferral to a 403b and/or 401k plan in a calendar year, then the excess (plus earnings on the amount overfunded through the date of correction) needs to be refunded by April 15th of the following calendar year. The overfunded amount plus earnings will be taxable in the calendar year overfunded but will not be subject to the 10% penalty when distributed from the plan back to you. The excess deferral and associated earnings distributed back to you are reported on a Form 1099-R.
Another consideration when you switch employers pertains to the retirement funds at your prior employer. You generally have the option of keeping those retirement funds invested in your former employer’s retirement plan.
Another option that may help simplify your tracking and management of your retirement funds over time, would be to instruct your prior employer’s retirement plan administrator to distribute the funds from that plan as a direct rollover into either your current employer sponsored retirement plan or into an Individual Retirement Account (IRA). Consolidating retirement accounts if you periodically switch employers will help you track to better track your retirement assets.