By Grace W. Weinstein

Married or single, old or young, you may need a will to direct how you want your property distributed after your death.

You should also update your will periodically to meet changes in tax law and personal circumstances.

On the tax law front, for example, the federal estate tax is scheduled to exclude larger and larger sums over the next several years until it disappears entirely in 2010. For this year, the exclusion is $1 million. By 2009, it will reach $3.5 million, an amount that will effectively remove most estates from federal taxation. However, unless the current law is changed, the estate tax reappears in 2011, with an exclusion back at the $1 million level.

Wills incorporating a credit shelter or bypass trust—a strategy often employed by married couples to ensure that the estate tax exclusion can be used by both partners—often place the amount of the exclusion in the trust when the first spouse dies. Such wills may need to be revised to reflect the new exclusion amounts.

Your estate will be subject to federal estate tax only if you leave an estate worth more than the amount excluded from federal estate tax. But state taxes may be an issue as many of the states— facing declining revenues along with the elimination of a tax credit that effectively offset the federal tax—are "decoupling" their estate taxes from the federal tax.

In practice, this means that some states have frozen the amount of the estate tax exemption for state tax purposes. Where $1 million is excluded from federal estate tax, for example, New Jersey has frozen its exemption at $675,000. If you live in a state differing from federal practice, you may want to consult a knowledgeable advisor about the need to revise your will. (You may want to consult the advisor regardless of state practice.)

Changes in personal circumstances are also appropriate occasions for reviewing and, if necessary, updating your will. You should definitely review your will if you get married, divorced, or remarried, or if you have children or grandchildren. All of these events can affect your choice of beneficiaries. You should also have a lawyer review your will if you move to another state. State laws differ, and your will should be in compliance.

You may want to review your will if your beneficiaries' needs change, as well. An elderly parent relying on your support may have passed away since you originally wrote your will, while a youngster who needed college money may now be a successful businesswoman.

Also check to be sure that the executor originally named to manage your estate is still able and willing to do the job. Your financial affairs may have become a lot more complicated over the years, and you may want someone with more financial savvy and administrative smarts than your original choice. You also need someone willing to do the time-consuming and often tedious tasks associated with being an executor.