If you do this, you're smarter than most millionaires

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Private companies have created vast wealth for millions of Americans. But as business owners start reaching the later stages of their careers, one survey showed many don't have a plan for passing down or selling their businesses.

In June, U.S. Trust released the results of its Wealth and Worth Survey, which sampled a group of millionaire business owners with at least $3 million in investable assets.

"A large number of business owners have not articulated a strategy for ensuring the highest possible valuation of the business or its continuity beyond the current owner," the report said.

The study found that nearly two-thirds of business owners do not have a succession plan, which could include either a sale or transfer of the company. Since most of the owners rely on their businesses for income, the lack of such planning means "their main source of income could be in jeopardy," according to the report.

Additionally, the results showed many owners failed to think about the future of their businesses beyond their own lives. Only 16 percent plan to pass the business on to their families, and 64 percent of older business owners (those over 50) have no formal succession plan.

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Many business owners, whose finances and identity are so closely tied to their companies, simply don't want to think about giving them up. According to the report, three-quarters of the millionaire business owners founded their companies and only 8 percent inherited them.

Many may intend to simply work well past retirement age.

"Many entrepreneurs never plan to stop working or they wait until they are ready to retire," the report said. "Others have a plan in mind that they may or may not have communicated, but leave its execution to chance by not formalizing it."

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Additional findings from the survey include the fact that younger millennial business owners are more likely to have succession plans than baby boomer owners, and women are more likely to have them than men.

"Succession planning is a crucial part of long-term business planning that helps prepare for a smooth, strategic exit by the owner or for an unexpected change in circumstance, such as illness, disability or divorce."

U.S. Trust, part of Bank of America's wealth management division, surveyed 640 high and ultrahigh net worth adults, 118 of whom are business owners. It had a confidence level of 95 percent.