Americans who will reach retirement age over the next two decades rely too heavily on Social Security when estimating future income, and many believe they are reasonably well versed on the countless and complex options available for claiming benefits. The financial-planning community, however, begs to differ. A survey released today by AARP and the Financial Planning Association reveals that roughly half of consumers ages 45 to 64 expect that Social Security will be a major source of their household retirement income, while 94 percent of certified financial planners say most of their clients will rely on Social Security for half or less of their retirement income. That includes 53 percent of CFPs who expect Social Security to provide 30 percent or less of their client's retirement income.

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"The average consumer seems to assume Social Security will represent a much larger proportion of their income in retirement than financial planners would estimate, which means they may have less incentive to aggressively save on their own, either through employer-sponsored retirement plans or independently," said Dave Yeske, a CFP and managing director of Yeske Buie. The survey, which included about 1,200 future Social Security beneficiaries and 1,300 CFPs, sought to compare the experiences and knowledge of consumers with the recommendations of professional financial planners. Read MoreTax credit can help you save

Nearly half of consumers surveyed indicated they were "somewhat knowledgeable" about how their Social Security benefits will be determined. However, a mere 9 percent considered themselves "very knowledgeable" about how benefits are determined. Survey questions revealed consumers are only somewhat knowledgeable about basic issues, such as the earliest age they can receive benefits and the ability to claim widow benefits. They are less knowledgeable still about the impact their claiming decisions will have on benefit dollar amounts, which could leave their nest eggs vulnerable as retirement day dawns. "For families and individuals looking to claim their Social Security benefits soon, this survey shows that far too many face a claiming knowledge gap, potentially leaving thousands of dollars on the table," said AARP president Jeannine English.



Money on the table

It's easy to see why. More than 8,000 claiming strategies exist for married couples alone. Financial Engines, a defined-contribution managed-account provider, estimates the average single retiree leaves more than $100,000 in lifetime benefits on the table by fumbling his or her Social Security choices. The average married couple, it reports, misses out on $250,000 or more. Read MoreDoes your retirement plan need a reality check?

The knowledge gap not only contributes to a loss of future benefits, said Ed Gjertsen II, a CFP and president of the Financial Planning Association, but also perpetuates poor decision-making regarding how much working Americans need to save during their peak earning years to maintain their standard of living during retirement. The survey found that just 1 percent of financial advisors believe their clients are very knowledgeable about Social Security benefits overall, and 31 percent say their clients are somewhat knowledgeable about claiming Social Security. According to the survey, future beneficiaries are also befuddled by the age at which they are eligible to collect Social Security.

While 61 percent correctly indicated the earliest age is 62, almost 2 in 10 believe they cannot collect before age 65 and another 9 percent believe they can claim prior to age 62. The opportunity to increase Social Security income by postponing benefits is yet another source of confusion for consumers. While 88 percent are aware that waiting until their full retirement age to collect (either 66 or 67 for the individuals surveyed) would increase their benefit amount, only 5 percent know the degree to which those benefits would increase by waiting additional years—25 percent to 30 percent, depending on their birth year. Nearly 3 in 10 financial planners recommend to clients that they wait to claim benefits until age 70, according to the survey, but only 13 percent of consumers plan to wait that long.

Financial planners and consumers also diverge on their outlook for Social Security solvency. CFPs were more likely (50 percent) to correctly identify 10 to 20 years as the length of time the social safety net would remain than consumers (27 percent) were; the latter thought it would be exhausted earlier. At the same time, it seems, divorcees may also be susceptible to Social Security snafus. Benefits for divorced Americans are available to unmarried ex-spouses if the couple was married for 10 or more years, but 34 percent of previously married respondents believed that a divorcee could collect off of the ex-spouse's work record if they were married five years or less, 26 percent correctly identified 10 years as the minimum duration, and 31 percent believe they could never collect Social Security benefits based on their ex-spouse, regardless of number of years married. (Spousal benefits are equal to one half of the ex's full retirement-age benefit if collected at full retirement age and less if collected earlier.) Read More3 easy ways to save for retirement

Such lack of clarity can result in an ex-spouse forgoing a higher benefit (or any benefit at all). To maximize the size of their future benefit, consumers must seek out reputable sources of information and consider all factors, including age, marital status, lifetime earnings and claiming strategies, said Gjertsen of the FPA. Apart from financial planners, he said, consumers can obtain guidance from such resources as AARP and the Social Security Administration, which has gotten far better at customer service. "It used to be that we'd call in to the Social Security office three times and hope to get two of the same answers, but the SSA is doing a much better job these days," Gjertsen said.

The average consumer seems to assume Social Security will represent a much larger proportion of their income in retirement than financial planners would estimate. Dave Yeske managing director of Yeske Buie