What should I do now in 2024 when I just realized I had over contributed to my 403b plan after I switched job in 2023?

[Taxhelpneeded2023]

I switched job in December 2023 and it resulted I over contributed $700 to the 403b plan from my new job. It's already past 4/15 so I can't just contact the plan admin to withdraw and to correct it. What is my action item to fix this now?

[dmertz · Accepted solution]

Assuming that this was an excess deferral contribution to the traditional account in the 403(b), the excess contribution must be reported on your 2023 tax return as Miscellaneous income, other income not already reported on a Form W-2 or Form 1099, Other, so that it appears on Form 1040 line 1h.  The excess will be taxed a second time when you eventually distribute money from your 403(b).  (Double taxation of the excess is effectively the penalty.)

[Opus 17]

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@dmertz wrote:

Assuming that this was an excess deferral contribution to the traditional account in the 403(b), the excess contribution must be reported on your 2023 tax return as Miscellaneous income, other income not already reported on a Form W-2 or Form 1099, Other, so that it appears on Form 1040 line 1h.  The excess will be taxed a second time when you eventually distribute money from your 403(b).  (Double taxation of the excess is effectively the penalty.)

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If you have not already filed, make sure you enter your W-2s correctly, because your 403b contributions are listed there and the program should register them automatically. Turbotax will be aware of the situation, inform you of the excess, and when you tell the program that you will not remove the excess, the program will add the income to line 1h. 

If you already filed, you need to file an amended return.  But because the 403b should be automatic as long as your W-2s are correct, I am thinking you have not already filed.