How to report excess deferral s 401k contribution?

You will not receive a 2024 form 1099-R.

Report excess salary deferrals (excess 401k contributions) returned to you after the end of the tax year but by April 15th of the following tax year on your 1040 as Wages.  Do not create your own 1099-R for this situation.

Page 11 of IRS Pub 525 under Excess deferrals (the IRS term for 401K contribution is deferral) tells us: 

If your deferrals exceed the limit, you must notify your plan by the date required by the plan. If the plan permits, the excess amount will be distributed to you. If you participate in more than one plan, you can have the excess paid out of any of the plans that permit these distributions. You must notify each plan by the date required by that plan of the amount to be paid from that particular plan. The plan must then pay you the amount of the excess, along with any income earned on that amount, by April 15 of the following year. You must include the excess deferral in your income for the year of the deferral. File Form 1040 or 1040-SR to add the excess deferral amount to earned income on line 1h.

What you earned will be covered by a 1099-R for the following tax year and will be entered then as a normal 1099-R.

Below is how to do this in TurboTax Online:

1. Click on Federal in the left-hand column, then on Wages & Income
2. Navigate to the list of income categories
3. Locate the section Less Common Income
4. Select Miscellaneous Income and click Start
5. Select Other income not already reported on a Form W-2 or Form 1099 and click on Start
6. Answer the question "Did you receive any other wages?  Yes
7. Click through the questions till you get to Any Other Earned Income
8. Answer Yes to Did you earn any other wages?
9. Indicate Other as Source of Other Earned Income and click Continue
10. For the description enter "2024 Excess 401K Deferrals" and click on Done