A statement signed by an independent accountant outlining his or her opinion regarding the quality of information contained in a company's financial reports and records. The subject of accountant independence became an important issue in the wake of the demise of such corporate giants as Enron and WorldCom in the early 2000's. (http://www.investopedia.com/terms/a/accountantsopinion.asp)

There are several other ways exist by which companies can influence the timing or the magnitude of reported free cash flows. Increasing the use of capital lease transactions as a way to acquire fixed assets obfuscates free cash flow because capital expenditures may be understated on a year-over-year basis. (Gitman, 2008).

Corporate accountants are able to manipulate their earnings to portray a more favorable earnings statement by implementing such techniques as recognizing revenue too early, delaying expenses and saving them for future years, overvaluing assets and undervaluing liabilities (Harper, 2014).

When companies get desperate to show earnings or reduce losses, sometimes they resort to fraudulent timing differences to show phony profits. By recognizing these often simple schemes CPAs can usually detect material financial statement frauds early, before they become catastrophic. (Wells, 2001).

Overvaluing assets involves underestimating obsolete inventory which lowers COGS and increases gross profit margins. Failing to write down or write off impaired assets keeps overvalued assets on the balance sheet which overstates profits until losses are finally recognized (Harper, 2014)

Playing with time, recording revenue when services are still due, Shipping merchandise before the sale is final are some of the earnings which can be manipulated by corporate accountants to differ the company earnings. (Wells, 2001).

References:

Gitman, J. (2008). Principles of