Box12c on my W-2 shows $6400.00 which is the HSA contributions. But my employer only contributed $1200 of that amount. I contributed $5200 thru payroll deductions.

[jimborum]

When entering 6400 from that box, it shows it all to have been contributed by my employer. It shows me having 0 deduction for my HSA.

[DanielV01]

You are correct.  Your employer is required to report it in this way if they were deducted pretax from your income.  In this case, you have already received the tax benefit because your income is already lowered on your w-2 by the amount of the payroll deduction you made to your HSA.  See this FAQ on Box 12 codes (note the explanation on code W):  https://ttlc.intuit.com/replies/3300234

[Opus 17]

 That is correct. All contributions made by payroll deduction are treated as if they were made by your employer. Basically, you  agree to a voluntary salary reduction, and your employer contributes that money to the HSA.  Since the money has already been subtracted from your taxable pay and has not been taxed, you cannot deduct it again.  But you have already gotten the maximum tax reduction by having it taken out of your paycheck before taxes.