At the end of an accounting period, a company has $ 4,000,000 recorded in accounts receivable, all

Question:

At the end of an accounting period, a company has $ 4,000,000 recorded in accounts receivable, all from sales. It is not likely that the company will collect all of the $ 4,000,000, even though all the sales really took place. Give three reasons that collections might not equal $ 4,000,000.