My employer contributes to my HSA each month (this is not taken from my income, it's an additional benefit, part of which health insurance option you choose). The total of these contributions are a bit less than the annual maximum contribution. I also choose to have a small amount withdrawn from my paycheck by my employer each month and contribute that in addition, to max out the contribution amount.
It is my understanding from reading the W-2 instructions and Form 8889 instructions that these contributions are both considered "employer contributions" and should be listed on my W-2 Box 12 with code W. By the way, boxes 1, 3, & 5 do not include these amounts.
This entry is missing on my W-2. Payroll say that it is their understanding it is optional for them to report it that way. Is this correct? This seems strange to me as there would be no way to trace where that money came from.
2017 tax season update: surprise, surprise, on this year's W2, they filled the employer contributions in correctly.