One of the biggest myths about Social Security is that everyone is entitled to benefits once they reach a certain age. In reality, Social Security benefits are earned by paying taxes on wages.

Specifically, it takes 40 lifetime work credits to qualify for Social Security, and the value of a single credit changes each year. If you don't work for more than a few years, or you don't work at all and therefore don't end up paying into Social Security, you may not be eligible for benefits once you reach retirement age.

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Thankfully, though, there's another way to qualify for Social Security in that scenario -- spousal benefits. But the rules regarding spousal Social Security benefits can be complex.

Here's what you need to know about spousal benefits and how they differ from retirement benefits claimed on your own earnings record.

Spousal Social Security benefits: A lifeline for some retirees

It's not so uncommon to reach retirement age without much of a work history -- or any work history, for that matter. If you were a caregiver for many years, you may have simply dedicated your life to unpaid work.

The good news is that if you're married or a qualifying divorcee, you may be entitled to spousal benefits from Social Security. But there are a few key things you need to know.

First, if you're still married, you can't file for spousal Social Security benefits until your spouse signs up. If you're divorced, you generally don't have to wait for your ex-spouse to file to get benefits yourself.

Second, the maximum amount a spousal benefit can be worth is 50% of the amount your spouse is eligible for at their full retirement age. If your spouse's full retirement age benefit is $2,500, you can't collect more than $1,250 in Social Security spousal benefits yourself.

This is an important thing to note, because when you're claiming Social Security on your own earnings record, you can accumulate delayed retirement credits for waiting beyond full retirement age. Those credits are worth 8% a year, and you can accrue them until you turn 70.

With spousal benefits, those credits don't apply. As such, there's no sense in delaying a spousal benefit claim past your own full retirement age, since it won't result in larger monthly checks.

Make sure you know the rules

Even though a common path to Social Security is earning enough money and paying enough taxes to qualify, you may be eligible for benefits simply by being married (or having been married) to a qualifying recipient. But it's important to know how spousal Social Security benefits work and how they differ from traditional retirement benefits.

It's also important to make sure you and your spouse are in sync on your Social Security claiming strategy, even if the only benefits you're entitled to are spousal benefits. That way, you can work together to make the most of that crucial income stream.