You can only deduct expenses you pay in 2023. You also generally can't deduct expenses you pay in advance for care in a future year, but that rule would not apply if you want to pay in advance in 2023 for a procedure that will be performed in 2023. Check with the facility and see if they will accept an advanced payment based on an estimate of the cost of care and your insurance coverage. (At my most recent elective surgery, the facility required advanced payment based on an insurance estimate. They had to refund me when the insurance share came in higher than expected.)
