Social Security is one of those things you probably don't spend a lot of time thinking about until you're close to retirement age. But the more you read up about the program, the better positioned you might be to snag more benefits -- and enjoy more financial freedom during your later years.

Also, the more you learn about Social Security, the less likely you'll be to make an inadvertent error that costs you money down the line -- like these.

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1. Expecting your benefits to cover your senior living expenses in full

Many seniors end up struggling financially in retirement because they live mostly or solely on Social Security. The reality is that those benefits are not designed to replace your pre-retirement paycheck in full. If you're an average earner, you can expect them to take the place of about 40% of your wages. And that's generally not enough to live on.

That's why it's important to be realistic about the amount of money Social Security will pay you -- and have a backup plan. That could mean building up a nest egg by saving in an IRA or 401(k) plan. Or it could mean continuing to work in retirement so there's money coming in on top of your monthly benefits.

2. Not knowing your full retirement age

Your full retirement age, or FRA, is when you're entitled to receive your complete monthly Social Security benefit based on your earnings record. It's essential that you know what your FRA looks like. If you don't, you might end up claiming Social Security early by accident and slashing your monthly benefits for life.

The Social Security Administration (SSA) will let you start receiving benefits as early as age 62 if you so choose. But for each month you start to collect benefits ahead of your FRA, they'll be reduced.

Some people intentionally claim Social Security early because they have personal reasons. And that's not always a poor choice.

But if you're going to file early, do so because you've put thought into the decision and realize it's the right one for you. You shouldn't claim your benefits early by accident or by not knowing your FRA.

FRA is based on your year of birth. Here's a table that will show you what yours is:

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.

3. Not reviewing your annual earnings statements

Each year, the SSA issues workers an earnings statement. Yours will summarize your wages for the year and give you an estimate of your future monthly Social Security benefit.

It's important to check your earnings statement each year because underreported income could result in lower monthly benefits down the line. For example, say you earned $95,000 last year but switched jobs midway through, so only half of your income somehow got reported to the SSA. That could make a big difference in your future benefits, so that's a mistake you'll want to correct. If you don't check your earnings statement, you won't know to correct it.

While Social Security shouldn't be your only source of retirement income, it might end up being a significant one, nonetheless. So it's best that you do what you can to avoid these mistakes at all costs.