quote:
You can get with HR and have them put your whole paycheck in. Beyond that, unless you have a bonus coming. There’s not much you can do unless you own the company.

I could be wrong, but I think if HR is worth their salt, he could write his company a check that then gets put back into the 401k for wages earned earlier in the year. He certainly can’t call up the 401k provider and do it. And I don’t think he can write a check to the 401k provider (not sure).
But I am almost positive that the only things that matter when it’s reviewed is that you have enough income on your w2 to justify the amount remitted by the company on your behalf to the plan, not whether the money went from them, to you, back to them, to the 401k or not.

It’s also possible HR just makes him withhold bigger portions of his future checks if it works because it’s easier, and if there’s enough income coming to cover the cost of what he wants to contribute, that’s almost certainly an easier option for all involved.

For the future, I have read/heard that some folks who own businesses will contribute their full amount on 1/1 or the first day the bank is open each year without having necessarily earned $20,500 by that date without any real consequences. I would not feel comfortable doing that. I probably should change my compensation up to include a January 401k bonus amount to front-load the account, but I have just deferred my first 2.5 (monthly) paychecks at 100% until the contribution is made in full- So OP, there are some crazy folks out there who contribute 100% of their paycheck to their 401k a few times each year. And there are a few strategies you can look into.

Congratulations on having a wonderful problem to solve. You are winning the game, it seems.