What's the Maximum retirement contribution. 401(k)/403(b)/457 combined?

You lose....

$31,000. the 401(k) is employee and the 457 is considered an employer contribution even if it's actually contributed by the employee. Here's the logic:

Treas Reg § 1.457-2(a) and (b)(1). Subsection (a) defines amount(s) deferred as annual deferral(s), which paragraph (b)(1) in turn explains is "the amount of compensation deferred under an eligible plan, whether by salary reduction or by nonelective employer contribution". Then go to IRC § 457(b)(2) where the amounts that may be deferred are limited to the lesser of the applicable dollar amount or the employee's compensation. Then IRC § 457(e)(15) limits applicable dollar amount to $15,500 (indexed).

So, the 457 contribution counts towards the IRC § 415 limit of $45,000 but does not get aggregated with the 401(k) deferral limit for 402(g) purposes which is the $15,500 deferral limit for 401(k) plans. However, 403(b) deferrels DO count towards that 402(g) limit because it's considered an employee contribution.

Hope this helped resolve the issue.

The combined max is the same as the max for one. For example, if the max is $15,500 with one, then you can put $15,000 in one and $500 in the other, or $8000 in one and $7500 in the other, but cannot put $15,500 in each. If you put the full $15,500 in either, then you cannot put anything in the other.

The max changes from year to year (due to inflation indexing) and depends on age. After a certain age, "catch up" contributions are allowed.