Entering $20K in Box 12, code BB from W-2 form has no effect on the federal income tax. Why? Isn't a contribution to a 403B tax deductible?

[Canuck-Habs]

Should the $20K entered in Box 12 BB reduce the taxable income on the W2 form? If I replace $20,000 with $0 (as a test), there is no effect on the Federal Tax Due. I thought a 403B contribution would reduce the taxable income.

[Ashby]

Not in your case because they are Roth contributions which mean they are after tax. Only pre-tax contributions lower your taxable income.

[Canuck-Habs]

So to be clear, contributions to a 403b are not tax deductible? <a rel="nofollow" target="_blank" href="https://www.investopedia.com/articles/retirement/10/top-9-benefits-403b-plans.asp">https://www.inves...>

[Ashby]

This is copied and pasted from your link:  Since 2006, employers have had the option to allow Roth contributions to 403(b) plans. Unlike a traditional IRA, Roth contributions are not eligible for a tax deduction.