Total of all your HSA’s? If you have more than one HSA, add them all up for this date. What about other HSA’s from previous employers?

Yes, add all HSA balances together plus any contributions that you have made in 2017 for the 2016 tax year. Include the HSA fund balance from the previous employers in the calculation.

Fund balances are generally reported on a Form 5498-SA, however custodians don't have to mail them until 5/31/17 (because you can still contribute up to due date of return).

Look to your statements or contact the custodian directly for the balance as of 12/31/2016.

What is interesting about this type of reporting is that if you are able to redirect HSA funds to investments they perform poorly the amount could go down without actually being used for any withdrawal for medical purposes.

Yes, this is true.