What is the overall combined 401(k) contribution limit including employer money?

Beyond your personal deferral limit, the IRS caps the total that can go into your 401(k) from all sources in a year, your deferrals plus employer match plus profit-sharing plus after-tax contributions, under Section 415(c). This overall ceiling is much higher than the employee-only limit and is also indexed annually, so check irs.gov for the current figure. Age-50 catch-up deferrals sit on top of even this combined limit.

This combined cap is what makes the mega backdoor Roth possible: after maxing your deferrals and receiving the match, any remaining room up to the 415(c) limit can be filled with after-tax contributions, if your plan allows them. High earners aiming to supercharge savings should know this number, since the match consumes part of the available space.