You probably know less about Social Security than you think.

More than two-thirds of older workers said they were confident about the rules of America’s largest retirement program, according to a new survey by Fidelity Investments.

Yet among the 521 people age 55 to 61 that Fidelity polled in October, most got these three key concepts wrong:

Give advance notice

To that point, 65 percent of people close to retirement didn’t know that you have to apply to the Social Security Administration three months before you receive your first benefits check. And 9 percent believed that the agency would contact them when it was time to receive benefits.

You are mostly on your own when it comes to Social Security notices. The SSA only sends out paper statements to people age 60 and over who aren’t receiving benefits and who don’t have a My Social Security online account.

My Social Security is the best place to learn the basics of the program, said David Freitag, a financial planning consultant at the MassMutual Financial Group. Freitag recommends people review their annual Social Security statements at least once a year.

Check to make sure the earnings record on your Social Security statement is accurate, especially for years where you’ve switched jobs. You can correct errors within three years, three months and 15 days following the year of the mistake. If you miss the deadline, it’s still worth it to try to fix the statements because the SSA has been known to cut people some slack.

Know your full retirement age

Fidelity found only 26 percent of older workers actually knew their full retirement age, or the age at which you can claim your benefits unreduced.

You can read the full article on CNBC here: