Social Security serves as an important income source for many seniors. And there's a good chance you'll end up falling back on your benefits to cover your living expenses in retirement.

The problem with Social Security, though, is that the program is loaded with rules. And if you don't know some of those rules inside and out, you could end up making some pretty poor decisions that hurt you financially over time. With that in mind, here are three such blunders you should really try to avoid.

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1. Not knowing your full retirement age

Social Security doesn't pay all seniors the same benefit. Rather, the amount of money you're entitled to during retirement will hinge on how much money you earned during your 35 highest-paid years in the labor force.

You're allowed to sign up for Social Security beginning at age 62. However, you're not entitled to your full monthly benefit based on your income history until you reach full retirement age, or FRA.

Just as Social Security doesn't pay a single universal benefit, FRA is not a universal age. Rather, it depends on the year you were born, as follows:

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 or later

67

Data source: Social Security Administration.

If you file for benefits before reaching FRA, expect them to be reduced. And if you sign up at the earliest possible age, 62, you should anticipate a significant reduction.

2. Not understanding the rules of claiming early

You might assume that if you decide to file for Social Security before reaching FRA, the reduction in benefits you face will be temporary. Not so.

If you claim Social Security before FRA, the monthly benefit you lock in could be the monthly payment you get stuck with for life. Granted, seniors on Social Security are eligible for yearly cost-of-living adjustments, so those could raise your benefit over time. But the base amount you start off collecting will be lower if you file early -- and your benefit won't be bumped up automatically once you reach FRA. (If that were to happen, there would effectively be no incentive for seniors to wait until FRA to file.)

3. Not undoing an early filing if the opportunity presents itself

Some seniors claim Social Security early and regret it after the fact. If that happens to you, you might assume that you're stuck with a lower monthly benefit for life.

Actually, that's not automatically the case. Social Security allows filers one do-over. If you sign up early but withdraw your benefits application within a year and repay all of the money you received, you can then file again later.

Many seniors don't realize this do-over option exists, though. As such, they miss out on the chance to claim a higher benefit after filing early. But if you act quickly enough, that doesn't have to happen to you.

The more you know about Social Security, the less likely you'll be to make poor choices with regard to your benefits. It pays to read up on the program as much as you can, especially if you're at an age when you might be claiming benefits in the not-so-distant future.