Checking my last day of health coverage

I was told my coverage ends on my last day, but the letter says the end of the month. I have read a lot of threads here and could not find my exact situation. I do not want to be surprised by a bill. How did you confirm your end date?

Keep a copy of any coverage confirmation in case of later disputes.

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