I am told to enter Box 12 for form 5498-SA but my W-2 has boxes 12(a), 12(b), 12(c) and 12(d). Which do I enter?

Form 5498-SA reports contributions to your Health Savings Account (HSA), Archer MSA, or Medicare Advantage MSA.

Don't enter this form into TurboTax; your account custodian sends it to you for informational purposes only. We recommend that you keep it with your tax return records.

The code from box 12 of your W-2 for HSA (Health Savings Account) is code W (Employer Contributions to Health Savings Account).

To understand Box 12 codes on your W-2 see FAQ below:

https://ttlc.intuit.com/replies/3300234