A health savings account is only available if you're covered by a high-deductible health insurance plan, but if you're allowed to contribute, you can save substantially on your taxes because of the tax benefits for contributing. However, how the contributions are reported on your W-2 depend on whether the contributions come out of your paycheck or your employer makes the contributions.
Form W-2 Codes
If your employer makes the contributions on your behalf or you make the contributions through a cafeteria plan, Code W will show up in box 12 of your W-2. A cafeteria plan allows you to make an election to have your employer withhold money from your paycheck and contribute it directly to the HSA. If, on the other hand, you make the contributions to your HSA on your own, your contributions won't show up on your W-2. Instead, you claim a deduction for them on your tax return.