Other frequent errors are of the mathematical variety.  The IRS receives reports of all your income from every source, and if you don't report everything they see, you can have a problem. That includes income from side jobs and investment income. For consultants and freelancers, it means income from every client.  Some taxpayers neglect to count all their charitable deductions, particularly in-kind donations of clothing, furniture and the like. Others take deductions that are too large for the goods they are donating. The IRS publishes guidelines for determining how to value your donations of goods, and it's best not to claim a $50 deduction for that old blouse from three seasons ago.  Life changes you have experienced over the past year—a child moving back home, an older relative moving in or a spouse rejoining the workforce—will affect your tax picture.  "More common and more commonly overlooked than tax law changes are life changes," Steber said. "All of those have huge pro-taxpayer implications."  (Read more: Boomers' aging parents may yield a tax deduction)  Most Americans are saving too little for retirement, and tax season is a great time to take steps to help eliminate the shortfall, said John Sweeney, executive vice president of retirement and investing strategies at Fidelity Investments.  According to its latest assessment of retirement savings, in which Fidelity surveyed 2.200 households, only 30 percent were saving adequately, and 40 percent were saving less than 6 percent of their salary—including employer matches. (Fidelity recommends a savings rate of 10 to 15 percent of salary.)  Until April 15, "you've got an opportunity to make a contribution to last year's retirement plan," Sweeney said. "It's a really good opportunity for people to do that."  Tax season is often when people consider converting a traditional IRA to a Roth IRA. Doing so requires you to pay taxes on the account now instead of in the future, when you take withdrawals. Though conversions make sense for many people, Sweeney warned against paying those taxes with IRA funds.  "Take the money out of a taxable account to pay the taxes on a Roth conversion," he said. That way you don't erode the amount of money converting to post-tax status.  (Read more: Roth vs. traditional IRA: Which is better?)
Form tax identity theft to deductions that may catch an auditor's eye, here are the most common taxpayer mistakes - and how to sidestep them.