I efiled my federal return using Turbotax but I later found that HSA contributions value on Form 8889 is blank though W2 reflects correct details. Do I need to amend my return to reflect right HSA contribution from W2 onto 8889 form? It is not going to change AGI or tax before and after amendment.
No, I would not amend if I were you. Just to let you know, the IRS is not yet accepting returns for processing as they are starting this on the 12th. So, technically, your return is sitting in a queue waiting for them to "take it in", so to speak. In addition, your W2 information is what they've also received so there will be no discrepancy at all that would be visible to them. They receive a W3 Form from your employer which details every W2 that the employer prepared and sent out to their employees prior to your receipt of your W2. You're all set!
if entered correctly, an HSA contribution showing on your w-2 (box 12 code w) should show up on line 9 of form 8889. all amounts put in your HSA, even those taken on of your paycheck, are code "w". because your taxable wages in box 1 of your W-2 have been reduced by your contributions you get no deduction on your tax return for them. however, form 8889 is required. at this point you can do nothing. most likely the IRS will discover the code W on the W-2 and the missing 8889 and send you a notice. at that point follow the instructions in the notice.