Whether its misinformation or plain old wishful thinking, most people thinking about retirement overestimate their future Social Security benefits payments, according to a recent survey by the Nationwide Retirement Institute.

The best way to prepare for your retirement so you’ll know exactly where you stand is to work with a financial adviser. People who do are much less likely to claim benefits early, leading to larger benefit payouts for years to come, the survey says.

“Social Security is a complex source of retirement income, often causing a disconnect between what consumers think their benefit will be compared to reality,” Tina Ambrozy, president of sales and distribution at Nationwide, said. “Preparing for retirement holistically by working with advisers and taking advantage of online tools can help older adults maximize benefits and achieve personal goals.”

The survey, released Wednesday, polled 1,300 adults who are already retired or will retire within the next 10 years. About 44% of respondents say Social Security will be their main source of retirement income, and about 23% said they’ll rely on a pension.

Less than one in 10 could identify all four factors that determine how much a person gets in benefits: work history, birth year, marital status and age at the time you start receiving benefits.

A whopping 70% of those surveyed believed they were eligible for full benefits much earlier than they actually are. The average retiree incorrectly thinks they’ll be eligible for full benefits at 63, rather than the full retirement age of 66. Another 26% incorrectly believe their benefits will increase once they hit full retirement age if they retire early.

The survey also shows that future retirees miss out on benefits by about $400 a month: They expect to receive $1,805 but current retirees receive $1,408, a 28% difference in what is expected compared to what is paid out.

One in three survey respondents work with a financial adviser, and they report about 15% more in earnings than those who do not. They’re also far less likely to draw benefits before full retirement age, and a staggering 90% of them say they are more able to do what they want in retirement, compared to 56% of respondents who didn’t work with an adviser.

Despite the fact that 44% of respondents say Social Security will be their main source of retirement income, two-thirds of future retirees worry the program will run out of money during their lifetime, and 40% believe there will be cuts under the current administration.

The Social Security and Medicare Trustees’ latest report showed trust funds will start coming up short by 2035 unless Congress does something. More than 80% of respondents say the system needs changing, and about half of those respondents say taxes should be increased on higher earners to boost the program’s funding.

The aforementioned higher earners say they should pay more in taxes to increase the plan’s funding, including 55% who have $250,000 or more in investible assets, and 48% of those with $1 million or more in investible assets.