I recomment a two (2) file system.
Label two manila folders for your file cabinet: EOB and HSA.
“EOB” stand for “explanation of benefits.” When you see a doctor, you do not pay at the time of service. The doctor submits a bill to the insurance company. The insurance company then sends you an explanation of benefits that tells you how much you should pay the doctor. Shortly after you receive your EOB, you will receive a bill from your doctor. The amount of the EOB should equal what the doctor bills you.
Put the newest EOB in the front of the folder. That way you will have a chronological history of medical services.
In this file you can keep your HSA statements. This way you will always know how much money you have in your health savings account. Local banks will often mail you a monthly statement that you can store in this folder.
If you use an online bank, it might be useful to print out copies of your statement on a quarterly basis and store in this file.
If you pay the medical bill by check, you can keep your checkbook in this folder.
This system will allow you to keep excellent records of medical costs. If you are ever audited by the IRS, you will have documentation that you used your health savings account for qualified medical expenses.