A chit is a tab or an IOU, a record of money owed. Your neighborhood deli might give you a chit the end of each week, letting you know how much you owe for your daily bagels.
A waiter at a restaurant often keeps a chit, adding up each item your group orders throughout the evening. There is also the kind of chit you keep when you're on an expense account, with your employer paying for hotels and meals — at the end of a business trip, you might turn in your chit so your boss knows exactly what the company's money was spent on. The root of chit is the Hindi word chitthi, "letter or note."