@dlt4
The “worst“ that could happen is that you would be required to pay the tax you owed for the disallowed deduction including a penalty and interest that adds up to about 1% per month backdated to the tax deadline for the year in question, which is usually April 15, plus an additional 25% penalty of the amount owed if the IRS determines that the this was a deliberate misstatement of your tax return rather than a misunderstanding.
As I mentioned before, if you are only obtaining the written care plan now, and you want to deduct your entire 2020 cost, you will have to judge whether you are comfortable with the risk.
