Look at the back of your room key. There is a long number there. Each individual room key will have the last two digits different. For example, my room key ended in 01 and my husband's ended in 02. The rest of the numbers were the same. When we got our bill, it was easy to see who charged what. That helped because there was one charge that we didn't understand but it was on my card. I rarely charge anything so it was easy to figure out what it was.