I have a 401a retirement account in lieu of Social security contributions. How do I add that back into turbo tax to correct the deficit of with holdings?

The employer contributions are automatically tax-deferred for federal income tax and federal income tax withholding purposes and exempt from Medicare taxes.

The employee contributions will normally not be tax-deferred.

You just report your W-2 income as you normally would and for boxes 3 and 4 of the W-2 will be left blank.

When you retire and start taking distributions on your pension, the amount you will paid in will be excluded from income tax.