How to put excess 401k contribution to 2019 contribution quota as I missed 2018 deadline to withdraw 401k over-contribution? how to file 2018 return?

[Rachel_W]

You cannot allocate your 2018 over contribution to 2019.  If you are unable to have your excess 401(K) Contribution refunded by 4/15/19, it will be taxed twice.....once on your 2018 Tax Return and then again in the future when you withdraw the funds.  Check out IRS Pub 525 for more details:  https://www.irs.gov/pub/irs-pdf/p525.pdf.

You should report the excess contributions to your 401(K) as Wages on Line 1 of your 2018 Tax Return by following these steps in TurboTax Online:

• Login to your TurboTax Online Account
• Click "Take Me to My Return"
• Click "Federal" from the left side of your screen
• Scroll down to "Less Common Income" and click "Show More"
• Select "Miscellaneous Income" and click Start or Update
• Select "Other income not already reported on a Form W-2 or Form 1099" and click on Start
  
• Answer the Question "Did you receive any other wages?  Yes
  
• Click "Continue" through the questions until you get to "Any Other Earned Income"
• Answer "Yes" to "Did you earn any other wages?
• Indicate "Other" as Source of Other Earned Income and click Continue
• For the description enter "2018 Excess 401K Deferrals" and click on Done