One advantage of not waiting until April 16 to start your taxes returns is that by starting in December you have a real opportunity for year-end tax savings when you can predict that you'll be paying taxes at a lower rate in one year than in the other. For example, under the right circumstances, deferring a year-end bonus or potentially accelerating deductions into the current year can pay off in a big way. Of course, to effectively plan, it helps to have a good idea of what next year's tax rates will be.