Income smoothing is the shifting of revenue and expenses among different reporting periods in order to present the false impression that a business has steady earnings. Management typically engages in income smoothing to increase earnings in periods that would otherwise have unusually low earnings. The actions taken to engage in income smoothing are not always illegal; in some cases, the leeway allowed in the accounting standards allows management to defer or accelerate certain items. For example, the allowance for doubtful accounts can be manipulated to alter the bad debt expense from period to period. In other cases, the accounting standards are clearly being sidestepped in an illegal manner in order to engage in income smoothing.
This practice is especially common in publicly-held companies, where investors are more likely to bid up the price of shares in a company that presents a reliable and predictable earnings stream over time.