How do you find your retirement income deduction amount on your W-2?

[Eric0]

Look for Box 12 and Box 13 on the W-2. The combination will indicate your retirement contributions - for example, 12D would be for elective deferrals to a 401(k).

The codes are all listed by the IRS with the W-2:

https://www.irs.gov/pub/irs-pdf/fw2.pdf