Employer health subsidy

As we head into a presidential election year, this subsidy will be a key topic in the broader discussion of health care reform.

Under the current tax exemption for employer-sponsored health insurance, your employer's portion of your health premium is tax-exempt. If, however, the subsidy is axed and your employer instead gives you a raise to cover those health costs, you'll have a higher taxable income or a higher tax bill, Gleckman said.

Education expenses

A deduction of up to $4,000 for qualified education expenses expires at the end of 2011. All or part of the amount you pay can be for classes beginning in 2012, Inman News reports. But you must make your payments in 2011.

More broadly, Obama's $467 billion in tax increases announced in September includes caps on tax deductions. The plan targets tax preferences, including those for savings accounts for higher education and health expenses.

However, many other tax credits, deductions and savings plans are still available for taxpayers to help with the expense of higher education. For more details, visit the Internal Revenue Service's education information center.

Transit commuter benefit

In November, Sen. Charles Schumer, D-N.Y., called for Congress to renew the federal mass-transit tax break. Many large employers offer transit-benefit programs that allow workers to set aside up to $230 a month of their salaries for mass-transit costs. The money is exempt from federal, state and city income taxes.

Schumer has introduced a bill to make the $230-per-month benefit permanent, The Associated Press reports. The latest extension of the benefit expires Dec. 31.

Mortgage interest deduction

To be clear, a Dec. 31 deadline is not approaching for this deduction. But with the housing market still weak, debate about how the U.S. government can support the housing market will continue into 2012.

Interest paid on a mortgage is tax-deductible if itemized. Roughly a quarter of all tax filers claim this popular tax deduction.

State sales tax deduction

The state sales tax deduction is scheduled to expire at the end of 2011.

This is a valuable tax break for residents of states without income tax -- Alaska, Florida, Nevada, South Dakota, Texas, Washington and Wyoming.

The timing of this deduction's end could wreak havoc on state and local budgets. They're already facing uncertainty about how much federal money they will get. Meanwhile, the weak economy and volatile stock market have lowered returns on state and local investments and will possibly cut income tax revenue. Adjusted for inflation, state and local revenues are below 2008 levels, said the TaxVox blog's Kim Rueben. Stay tuned.

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Internet sales tax, use tax

While there's no looming Dec. 31 deadline related to sales tax, this tax issue made our list because it will continue to be newsy into 2012. Amazon.com has agreed to start collecting sales tax from its California customers in September 2012 unless there's federal legislation on the matter, The New York Times reports.

As bricks-and-mortar stores struggle, legislatures beyond California have seized on the sales tax issue. Meanwhile, most states now have a use tax that requires consumers to pay taxes every April that retailers did not collect, although taxpayers rarely do so, said the Urban Institute's Gleckman.