Employer missed 401k contributions - what to do on tax return?

It seems like this should be treated as if your salary was reduced by the amount of the deductions that were never deposited. You didn't receive the income, so you don't report it as wages.

If Box 1 of the OP's W-2 already excludes the contributions in question he can't do what you say because that would be double-dipping.

What he probably should do is contact his state's Department of Labor about this.

The key question here is to figure out if the wages that were deducted and not deposited were included on the W-2 form. If the W-2 is correct and the 401(k) contributions are NOT included, then there isn't really any issue with the tax return, and it just needs to be straightened out with the employer.

If the wages that were not deposited in the 401(k) ARE included on the W-2, then you will need to make adjustments like Barry suggests. You should also try to get the employer to issue a corrected W-2 as well.

Now, whether the employer will be able to make appropriate retroactive changes in the deposits is another question. I don't know enough about the regulations governing 401(k) programs to know if this will be allowed, or if they would have to just pay out the wages. But if that happens, I would expect it to be income in the year you receive the reimbursement.

Time to let the pros chime in.