A month and a half into 2010 and Congress’ failure to stop the lapse in estate tax is still making waves. These two trusted news sources explain why having “no estate tax” this year should worry you.

One of the first reasons you should be worried, as revealed by this article in the Wall Street Journal, is that a larger base of estates will actually end up paying more this year rather than less; “Under last year’s law, estates up to $3.5 million, or $7 million for married couples, were exempt from federal tax. This year that law has been replaced by a fiendishly complex levy raising taxes on the assets of those with little as $1.3 million. It will affect the heirs of at least 50,000 U.S. taxpayers who die this year, whereas the old law affected only about 15,000 estates a year.”

Another main cause of worry, explains the New York Times, is the possible reinstatement of the estate tax by congress, effective retroactively; “The general view is that Congress wants to, and should, re-enact the estate tax retroactive to the beginning of this year,” [says tax specialist Ian Shane] “In January, February or March that’s easy, but as the year goes on it becomes more difficult.”

Of course the biggest worry estate planners have is the effect this year-long lapse will have on existing plans. Couples who already have an existing estate plan are advised to get their documents reviewed—and possibly revised—to prevent “standard clauses” from having unanticipated effects. As Joanne Johnson, head of the American wealth advisory service of J. P. Morgan explained to the NY Times, “It’s common to find language like ‘I hereby fund this trust to the maximum amount I can shelter from federal estate tax.’ The rest can then pass tax-free to the spouse. Such wording is risky as long as the estate tax is off the books… because there is no maximum.” What ends up happening is that everything goes into the trust for the kids, leaving the spouse with nothing.

What is the lesson here? The lapse in the estate tax may not be the boon it first appears to be. Talk with your estate planning attorney to find out how the new laws may affect your family.