I enrolled in an HSA and made a pre-tax contribution of $3,350 through payroll deductions.
This should be included in 12W of your w-2. salary reduction is proper because that's where you get the tax deduction when you make HSA contributions through an employer plan.
Additionally, my employer contributed $500 pre-tax to my HSA account.
that should be added to your contributions and $3850 should be in box 12W
box 9 on the 8889 should reflect 3850
you need to contact your employer to get a correct the W-2 and since yours is wrong most likely the W-2 for every other employee that made an HSA contribution through the employer is wrong.
from w-2 instructions
W—Employer contributions (including amounts the employee elected to contribute using a section 125 (cafeteria) plan) to your health savings account. Report on Form 8889.
if your employer refuses you'll have to contact the iRS
see this iRS link
https://www.irs.gov/faqs/irs-procedures/w-2-additional-incorrect-lost-non-receipt-omitted
calling instructions
- Call 1-800-829-1040 between the hours of 7:00 AM – 7:00 PM local time.
- Press “1” for English or “2” for Spanish.
- Press “2” for “answers about your personal income taxes.”
- Press “1” for “questions about a form you have already submitted or a payment or to order a tax transcript.”
- Press “3” for “all other questions about your tax history or payment.”
- Press “2” for “all other questions about your tax history or payment.”
- Do not input your Social Security Number when the recording tells you to.
- Press “2” for “personal- or individual-tax related question.”
- Press “3” for “all other inquiries.”
- Wait to be connected to someone at the IRS.
