Difference between Code W and Code DD in box 12 of Form W-2

[palfonso2]

In some posts, I see the following explanation for code DD:
"Box 12 amounts with the code DD signify the total cost of what you and your employer paid for your employer-sponsored health coverage plan."

In other posts, I see the following explanation for code W:
"Both the employer and pre-tax employee HSA contributions made through payroll are reported on the Form W-2 in Box 12 with Code W."

Based on these explanations, I don't see a clear difference.
Anyways, in my W-2 form, there is a huge difference in the amount.
Code DD amount is much higher than Code W amount.

Can you please clarify the difference?

[AnnetteB6 · Accepted solution]

Code (DD) is reporting the cost of your health insurance, in other words it is reporting the premiums that were paid for your health coverage.

Code W is reporting contributions made to your Health Savings Account (HSA).  The HSA is related to your health insurance based on the type of health insurance plan you have.  HSAs are used to help you save for and pay your out-of-pocket medical expenses that your health insurance plan does not cover, such as amounts you must pay to meet the deductible.

To learn more, see the following TurboTax help article:

What is a health savings account (HSA)?
 

[Opus 17]

DD is the premiums paid for your insurance.  W is the amount contributed to a health savings account.  Totally different. 

[DoninGA]

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.

DD—Cost of employer-sponsored health coverage. The amount reported with code DD is not taxable