I worked for a US company that gave you an accrual of one sick day every month, with a maximum accrual of 120 days on the books. Sick days could be "verified"

I worked for a US company that gave you an accrual of one sick day every month, with a maximum accrual of 120 days on the books. Sick days could be "verified" by presenting a doctor's note when you come back to work, or unverified, although you could only take up to five unverified sick days per calendar year. If you should use no sick days in a given calendar year, regardless of doctor's note or not, you would earn an additional vacation day for use in the following year. This set up a perverse incentive -- suppose you get sick, use some sick days, and bring back a doctor's note with you for it. You've lost your free vacation day for the next year, and you still have 5 allowable "unverified" days. You may as well now just "call in sick" on a few Fridays here and there to fill out your unverified sick day allowance, and give yourself some three day weekends.