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For HSA purposes, expenses incurred before you establish
your HSA aren’t qualified medical expenses. State
law determines when an HSA is established.
You can establish your HSA in accordance with the trust laws of the state that governs your account.
Under the estate laws of 49 states (CO included) , you can establish your HSA at any point after you become HSA eligible.
Most states require that, to establish a trust, an individual must:
• signal an intent to open a trust
• name a beneficiary
• place corpus – or something of value – into the trust
can 't say that's what CO law is regarding establishing a trust. either research it yourself (it's a legal issue) or contact an attorney in CO.