Did you request a filing extension before the original April 18 deadline?
The consequence of making excess contributions is that the excess is added back to your taxable income. This should be done automatically by Turbotax, although I believe it may not.
@Hal_Al @dmertz
You can leave the money in the 401(k), but it will be taxed when you withdraw it. Since it is also taxed now, that's double taxation, and most people would want to avoid that by removing the excess (which you have to pay tax on now regardless) and investing it somewhere else.
You only have until April 15 to remove any excess. This deadline is fixed in the law even if the tax deadline is later and even if you get an extension.
You have until the filing deadline to remove the excess. You would contact the plan, not your employer. If you did not get an extension, then the deadline is past and it is too late to do anything (even if you have't filed your return, you are past the deadline). You pay tax now on the excess (because it is not allowed to be contributed tax-free) and you will pay tax again whenever you withdraw the money (usually when you retire). If you did get an extension, you have until October 15 to contact the plan trustee and have the excess removed and paid to you.
Either way, the excess deferred salary must be added back to your taxable income. I have asked a couple other experts who can help you determine if you did that already or if you need to amend.
