There's a lot of mystery surrounding Social Security. How are benefits calculated? (There's a specific formula, but it's complicated.) Will benefits be cut in the future? (It's possible, though some lawmakers will work tirelessly to avoid having that happen.)

But one thing that should be pretty clear with regard to Social Security is when you're allowed to collect your benefits in full. Yet most people don't know when they're entitled to their full monthly benefit, reports Nationwide, and that lack of knowledge could lead to a host of bad decisions.

Social Security cards

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You must know your full retirement age

If there's one thing you really need to know about Social Security before signing up for benefits, it's your full retirement age, or FRA, which is when you can collect your monthly benefit in full. FRA is not the same for everyone. Rather, it depends on your year of birth, as per this table:

Year of Birth

Full Retirement Age

1943-1954

66

1955

66 and 2 months

1956

66 and 4 months

1957

66 and 6 months

1958

66 and 8 months

1959

66 and 10 months

1960

67

Data source: Social Security Administration.

Nationwide reports that 97% of millennials, 90% of Gen Xers, and 80% of baby boomers could not correctly identify their full retirement age, so if there's one number you must commit to memory prior to claiming benefits, it's that.

What happens if you claim benefits outside of FRA? Well, it depends when you file. You're eligible to first sign up for Social Security at age 62, but for each month you claim benefits ahead of FRA, they automatically get reduced on what's generally a permanent basis. Of course, the closer you are to FRA, the less of a hit your benefits will take, but if you're entering retirement with little in the way of savings, filing early is something you may want to avoid -- and knowing your FRA will help you do just that.

Incidentally, you're also allowed to delay your Social Security filing past FRA and claim benefits at a later age. For each year you hold off beyond that point, your benefits get an 8% boost, up until age 70. That means you have an opportunity to increase your monthly Social Security income by up to 32%, assuming you have an FRA of 66. With an FRA of 67, the maximum boost you can get is 24%.

Get schooled before claiming your benefits

Of course, your full retirement age is only one of many things you should know about Social Security before signing up. You should also, for example, know what your estimated monthly benefit based on your wage history look like. You can get that information on your annual earnings statement, which you'll receive in the mail if you're 60 or older or can otherwise access on the Social Security Administration's website. But if you don't know the age at which you're entitled to that benefit in full, you'll be doing yourself a major disservice -- one you may end up sorely regretting if it creates a scenario where you're overwhelmingly cash-strapped for the bulk of your retirement.