What are the tax penalties for going over the 401-k non taxable with holding limits?

I worked for two different companies and contributed to their 401-k plans. In the first one I contributed about $3500. I just saw in my last statement from my current employer I have contributed $17,250. I am over 50 and wanted to contribute the max of $20,500. Even though I stopped my contributions when I realized I was over the ammount. They said it may take another pay check with a deduction before it will stop. How can I get the overage back out of the plan and into my payrole. I must not be the only one this happens to so what does the IRS do if I am over? Thanks

Actually, it depends on if your 401(k) Plan allows for after-tax contributions or not. Contact your Plan administrator to be sure.

If so, then it gets added to your individual account. However, be aware that you might be subject to the same rules with penalties for early distributions, etc. (Again, contact your Plan Sponsor for more details. Each Plan is different.)

If not, then they should be refunding the money back to you, probably through payroll.

There should be no penalties to you.

No penalties. It's just post-tax money put into your 401k after the allowance amount. You should put the extra money in a Roth IRA if your income allows or just put it in a nonretirement investment account. Putting additional money above the taxfree amount in a 401k plan serves no purpose other than just limiting your investment options, which isn't a good thing.