Sep max contribution

The amount of salary deferrals you can contribute to retirement plans is your individual limit each calendar year no matter how many plans you're in. This limit must be aggregated for these plan types:

The maximum amount that you can contribute (salary deferrals) to a SEP or other retirement plans is your individual limit for each calendar year, regardless of how many plans that you are participating in. You would need to aggregate your contributions to the various plans to determine and ensure that you haven't exceeded the individual limit for that particular calendar year.

Here is a link to an IRS topic on the subject:

https://www.irs.gov/retirement-plans/how-much-salary-can-you-defer-if-youre-eligible-for-more-than-one-retirement-plan