The new levies, which take effect in January, include an increase in the payroll tax on wages and a tax on investment income, including interest, dividends and capital gains. The Obama administration proposed rules to enforce both last week.

Affluent people are much more likely than low-income people to have health insurance, and now they will, in effect, help pay for coverage for many lower-income families. Among the most affluent fifth of households, those affected will see tax increases averaging $6,000 next year, economists estimate.

To help finance Medicare, employees and employers each now pay a hospital insurance tax equal to 1.45 percent on all wages. Starting in January, the health care law will require workers to pay an additional tax equal to 0.9 percent of any wages over $200,000 for single taxpayers and $250,000 for married couples filing jointly.

The new taxes on wages and investment income are expected to raise $318 billion over 10 years, or about half of all the new revenue collected under the health care law.

Ruth M. Wimer, a tax lawyer at McDermott Will Emery, said the taxes came with “a shockingly inequitable marriage penalty.” If a single man and a single woman each earn $200,000, she said, neither would owe any additional Medicare payroll tax. But, she said, if they are married, they would owe $1,350. The extra tax is 0.9 percent of their earnings over the $250,000 threshold.

Since the creation of Social Security in the 1930s, payroll taxes have been levied on the wages of each worker as an individual. The new Medicare payroll is different. It will be imposed on the combined earnings of a married couple.

Employers are required to withhold Social Security and Medicare payroll taxes from wages paid to employees. But employers do not necessarily know how much a worker’s spouse earns and may not withhold enough to cover a couple’s Medicare tax liability. Indeed, the new rules say employers may disregard a spouse’s earnings in calculating how much to withhold.

Workers may thus owe more than the amounts withheld by their employers and may have to make up the difference when they file tax returns in April 2014. If they expect to owe additional tax, the government says, they should make estimated tax payments, starting in April 2013, or ask their employers to increase the amount withheld from each paycheck.

In the Affordable Care Act, the new tax on investment income is called an “unearned income Medicare contribution.” However, the law does not provide for the money to be deposited in a specific trust fund. It is added to the government’s general tax revenues and can be used for education, law enforcement, farm subsidies or other purposes.

Donald B. Marron Jr., the director of the Tax Policy Center, a joint venture of the Urban Institute and the Brookings Institution, said the burden of this tax would be borne by the most affluent taxpayers, with about 85 percent of the revenue coming from 1 percent of taxpayers. By contrast, the biggest potential beneficiaries of the law include people with modest incomes who will receive Medicaid coverage or federal subsidies to buy private insurance.

Wealthy people and their tax advisers are already looking for ways to minimize the impact of the investment tax — for example, by selling stocks and bonds this year to avoid the higher tax rates in 2013.

The new 3.8 percent tax applies to the net investment income of certain high-income taxpayers, those with modified adjusted gross incomes above $200,000 for single taxpayers and $250,000 for couples filing jointly.

David J. Kautter, the director of the Kogod Tax Center at American University, offered this example. In 2013, John earns $160,000, and his wife, Jane, earns $200,000. They have some investments, earn $5,000 in dividends and sell some long-held stock for a gain of $40,000, so their investment income is $45,000. They owe 3.8 percent of that amount, or $1,710, in the new investment tax. And they owe $990 in additional payroll tax.

The new tax on unearned income would come on top of other tax increases that might occur automatically next year if President Obama and Congress cannot reach an agreement in talks on the federal deficit and debt. If Congress does nothing, the tax rate on long-term capital gains, now 15 percent, will rise to 20 percent in January. Dividends will be treated as ordinary income and taxed at a maximum rate of 39.6 percent, up from the current 15 percent rate for most dividends.

Under another provision of the health care law, consumers may find it more difficult to obtain a tax break for medical expenses.

Taxpayers now can take an itemized deduction for unreimbursed medical expenses, to the extent that they exceed 7.5 percent of adjusted gross income. The health care law will increase the threshold for most taxpayers to 10 percent next year. The increase is delayed to 2017 for people 65 and older.

In addition, workers face a new $2,500 limit on the amount they can contribute to flexible spending accounts used to pay medical expenses. Such accounts can benefit workers by allowing them to pay out-of-pocket expenses with pretax money.

Taken together, this provision and the change in the medical expense deduction are expected to raise more than $40 billion of revenue over 10 years.

Article source: http://www.nytimes.com/2012/12/09/us/politics/new-taxes-to-take-effect-to-fund-health-care-law.html?partner=rss&emc=rss