How do I file HSA contributions with family HDHP coverage when I had Medicare Part A only?

[NCperson]

@teresagonzales you can't.  You are ineligible for HSA contributions.  Any contributions are considered "excess" and must be withdrawn. 

[MindyB]

If you have both an HDHP and Medicare Part A, you must not contribute to a Health Savings Account (HSA). 

While you can keep your HDHP and use Medicare as secondary coverage, the IRS considers Medicare "disqualifying coverage" for the purpose of HSA tax advantages. 

However, you can still spend the existing funds in your HSA tax-free for medical expenses.

If you already contributed, you can withdraw the excess before the filing deadline to avoid the 6% penalty.