Code D (single D) is for contributions to a 401(k). Whether you have those or not, you should also have Box 12 amounts for your combined employer & pre-tax employee HSA contributions ($5,000) with code W *and* the total value of your HDHP (premiums or actuarial value) with code DD (double D); none of those should be included in Box 1. If you don't have W or DD amounts, or if the single-D amount is NOT for 401(k) contributions, your employer needs to fix your W-2.
