Can i take a medical deduction for payments to a rehabilitation facility for my son??

If your son is being claimed as a dependent on your own tax return you can enter the amount you paid to the facility as a medical expense.   Are you claiming him as a dependent?

You may be able to take a deduction for rehabilitation expenses for your son if you claim your son as a dependent on your tax return and they are medically necessary and unreimbursed.

Note: You are required to itemize deductions, and the deductible amount are the costs exceeding 7.5% of your Adjusted Gross Income (AGI).

See Are Medical Expenses Tax Deductible? - TurboTax - Intuit.

You are also eligible to take a deduction for medical expenses you pay for your son even if your son is not a tax dependent, as long as the only reason they are disqualified is their income.

This is a bit tricky.  To claim an adult child as a dependent they must pass all the following tests,

1. person is a US citizen or lives in the US
2. person does not file a joint married return with a spouse, or if they file a return, it is only to claim a refund of withholding and they claim no other deductions or credits.
3. person is not a dependent of someone else
4. you pay more than half their total financial support for the year
5. their gross taxable income for the year is less than $5200 (for 2025).

If they meet all these tests, you can claim them as a dependent and deduct their medical expenses that you pay.  If they meet all the tests except the gross income test, you can't claim them as a dependent but you can still deduct medical expenses that you pay for them.

If they don't meet all the tests (or tests 1-4) then you can't deduct their medical expenses.