Just filed taxes and forgot to claim 401k contribution

[DavidS127]

Your next steps depend on whether your filed return is accepted or rejected by the IRS.

If your return is rejected, you can simply add your 401(k) contribution before you re-submit your tax return.

If your filed return is accepted by the IRS, you will need to file an amended return to add your 401(k) contribution. 

You should wait until your already-filed tax return has been processed (i.e., refund received or payment deducted from your bank account). Then, you can use TurboTax to prepare an amended return.

Click this link for instructions on how to file an amended return with TurboTax.

[dmertz]

Unless you are self-employed, the only entries you make in TurboTax regarding your 401(k) contribution is entering the items shown in box 12 of your W-2 only in box 12 of TurboTax's W-2 form, nowhere else in TurboTax.  If you did that, you did not forget anything related to your 401(k) contributions.

[ajkait]

What is the reasoning behind waiting until the return has been fully processed, rather than just update it as soon as it has been accepted and the 1040-X is available?

[CatinaT1]

If the IRS makes any changes to your return before it is fully processed, your amendment would be incorrect and would slow the process down immensely.  Of course you never anticipate the IRS to make changes, but it is not worth the headache you would create by filing an amendment too soon.

[ajkait]

That makes sense!