There's a good chance Social Security will end up playing an important role in your retirement. So it's important to know what benefit you're looking at before that milestone arrives.

Some seniors are pleasantly surprised to see a higher Social Security benefit than anticipated. But here are three reasons why your benefit could end up disappointing you big time.

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1. You didn't work a full 35 years

Social Security benefits are earnings-based. Specifically, your 35 highest-paid years in the workforce are accounted for in that calculation, with earlier earnings getting adjusted for inflation.

But if you don't have a full 35 years of work under your belt, for each year you're without an income, you'll have a $0 factored into your personal benefits equation. And so if your career only spanned 20 years, you can expect a much lower benefit as a result.

2. You claimed benefits before full retirement age

You're entitled to your full monthly benefit based on your specific earnings history once you reach full retirement age, or FRA. You're allowed to sign up for Social Security as early as age 62. But filing prior to FRA will result in a permanent hit to your benefit.

That's why it's important to know your FRA ahead of retirement. You can check out this table to look up your FRA based on your year of birth:

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. You're only entitled to a spousal benefit

To qualify for Social Security benefits, you need to accrue 40 work credits in your lifetime, and at a maximum of four credits per year. The value of a credit can change from one year to the next. Right now, a credit is worth $1,470 of earnings, and in 2022, it will take $1,510 to earn a single credit.

If you didn't accumulate enough work credits to be eligible for a monthly retirement benefit, but are or were married to someone who is, then you may be in line for a spousal benefit. That's the good news.

The bad news, however, is that your spousal benefit will amount to just 50% of what your current or former spouse is entitled to. And if your spouse isn't looking at a very high benefit, then you could end up with a benefit that isn't much to write home about.

Be prepared

You may need Social Security to carry you financially through retirement. Now that you're aware of some of the factors that could lower your benefit, you may be able to take steps to avoid a hit. That could mean making sure to put in 35 years in the labor force and not filing for benefits before FRA.

Now it may be too late to earn enough work credits to qualify for a benefit of your own. But if that's the case, and you're still married, have your spouse access a recent Social Security earnings statement for an estimate of his or her benefit. That way, you'll at least know what sort of paycheck you're in line for.