Chances are, clients who come to you with estate planning questions assume that a will is all they need to control their estate after death. But oh, how wrong they are.

A will doesn't control one of a client's most significant assets—retirement accounts. Instead, a veritable jungle of IRS regulations determine what your clients' beneficiaries will actually pocket from your clients' retirement accounts and when. The regulations are typically far too complex for clients to navigate on their own—and even experienced financial advisors can overlook some of their subtleties. As a result, beneficiaries may get saddled with huge tax bills that could have been avoided.

Fortunately, the IRS-takes-all scenario is avoidable through effective estate planning for retirement accounts while your client is still alive. Beneficiaries won't be the only ones to come out ahead. Protecting assets for another generation could mean years of continued financial relationships for your institution.

Total U.S. retirement accumulations reached $16.4 trillion last year, an all-time high and an 11% increase over 2005, according to the Investment Company Institute, a mutual fund trade group in Washington, D.C. Wirehouse advisors are likely to encounter more estate planning challenges related to retirement accounts as the national accumulations continue to grow, according to Ed Slott, an IRA distribution expert and author of Your Complete Retirement Planning Road Map. "At some point advisors will be judged not only on how much they made their clients, but on how much the family kept," Slott says. "The focus just can't be on building the account. You have to withdraw it, too—and often beyond more than one generation," he adds.

Estate planning clients who consult wirehouse advisors about their IRAs and qualified retirement plans have often completed the initial phases of wealth accumulation and are now contemplating the smartest way to transfer that wealth to children and other loved ones. Unfortunately, most people have virtually no idea of how to proceed with that task. "The money is in, but there is often no plan to get it out," Slott says. "The estate planning game for retirement assets requires the ability to work your way through a labyrinth of tax rules."

Retirement-account estate planning strategies vary wildly, depending on numerous factors, such as how much money the account owner needs for his or her own retirement. The ages of beneficiaries and their projected life expectancies may also help determine how to stretch distributions of tax-deferred investments so the account can accrue for generations. Whatever your client's situation, five potential pitfalls could determine whether the IRS or your client's intended beneficiaries will be the ultimate recipients of his or her retirement funds. These are problems that even seasoned practitioners may occasionally overlook.

And bear in mind that even if these estate planning mishaps are unlikely to occur on your watch, chances are excellent that clients will ask you to help reverse other advisors' mistakes that play out decades later, when the account holder dies and the IRS comes calling.

Pitfall #1: There's no contingent beneficiary.

Beneficiary designation forms are a critical, no-brainer necessity for effective estate planning. However, they are also a paperwork hassle that many clients—and even advisors—can't be bothered to revisit every few years. "It's easy to look at them as an afterthought—as busywork, or not important," says David Ness, president of Raymond James Trust Cos., in St. Petersburg, Fla. "But the client and the advisor both have to take beneficiary designations very seriously," he says.

A missing beneficiary could cost a client the ability to stretch distributions among beneficiaries for decades after his or her death, while the account funds continue to accrue tax-deferred. Most clients appoint a primary beneficiary, but a few still manage to overlook the detail. Diane Wilkie, an estate planning attorney and certified financial planner in Hempstead, N.Y., recently advised a client on planning for a taxable estate and learned that he had never appointed any beneficiary for a $200,000 IRA.

Many accounts include primary beneficiaries but lack contingent beneficiaries—a fact that may not be evident until the account holder dies. Sometimes the client can't decide on a contingent beneficiary and leaves the space blank. Or perhaps the contingent beneficiary has died. Either way, if the primary beneficiary is no longer alive, the account defaults to the owner's estate. Then you must determine which IRS distribution rule applies to the account.

Helen Modly, CFP, a financial planner for Focus Wealth Management in Middleburg, Va., says: If the owner was already taking minimum required distributions, the account must then be distributed as rapidly as dictated by the distribution method in effect at the time of death. But if the owner was not yet taking distributions, the account must be completely distributed within five years. Distributions would be taxable as income and included in the owner's taxable estate. Any possibility of stretching distributions is extinguished.