Behind the scenes, the IRS already has a well informed idea of how much you owe, based on the information submitted to them by your employer and a few select th

Behind the scenes, the IRS already has a well informed idea of how much you owe, based on the information submitted to them by your employer and a few select third parties - such as your bank or broker. I will corroborate, as I've posted elsewhere in this thread. I've had to interact with IRS employees, and they basically have all the information in their computer system. For simple returns, they could tell you the entire contents of it!