Checking my last day of health coverage - what worked for you?

I am not sure what date my benefits stop after being let go as a data-entry clerk. This is my first time dealing with any of this. The letter is unclear about dental and vision. What should I do about appointments?

Keep everything in writing and save the confirmation numbers. It saved me later.

Ask HR to confirm the exact date in writing. I also called the insurance company to double-check.