Social Security isn't something you're entitled to just because. You need to earn your benefits by paying taxes on wages throughout your career. What if you only work for a handful of years, or spend most of your life as a part-time worker? Here's what you need to know about Social Security eligibility.

It's all about work credits

When you make money and pay Social Security taxes on it, you earn work credits. The amount of earnings you'll need to earn a work credit changes from year to year. In 2020, for example, you get one work credit per $1,410 of earnings. In 2021, you'll need to earn $1,470 to get one work credit.

The maximum amount of work credits you can earn per year is four, regardless of how high your income is. Meanwhile, you need a total of 40 work credits in your lifetime to qualify for Social Security benefits based on your personal earnings history. You can accumulate those credits a number of ways, though. For example, you could work for 10 years and earn four credits per year for a total of 40, or you could work very part-time for 20 years and earn two credits per year, also totaling 40.

Female supermarket cashier

Image source: Getty Images.

Keep in mind that as long as you pay Social Security taxes on your income, it can count toward work credits. In other words, if you do freelance work but pay taxes on that income, it counts the same way a salary would.

Your Social Security benefits are calculated based on your lifetime earnings. That formula counts your 35 highest-paid years of wages when determining what monthly payout you're entitled to. For each year within that top 35 that you don't have an income on file, you'll have a $0 factored into your benefits calculation. This means if you only work 10 years and accrue just enough credits to be entitled to benefits, but then have 25 years of $0s going into your personal benefits formula, you won't end up with a very large payout (though thankfully, there's a minimum benefit you'll be entitled to).

What if you don't have enough work credits to claim Social Security?

If you don't accrue enough work credits in your lifetime to collect a Social Security benefit, that doesn't mean you're out of luck. If you're married to or divorced from someone who's entitled to benefits, and meet other eligibility criteria, you can still get a nice payout from Social Security in the form of spousal benefits. Spousal benefits are worth up to 50% of the amount your current or former spouse is eligible to collect. In other words, if your spouse is entitled to a $1,600 monthly Social Security benefit, you could be in line for an $800 monthly benefit at full retirement age.

Know the ins and outs of Social Security

Social Security is a pretty complex program, and the specifics of its rules can change from year to year (for example, the amount of earnings needed for a single work credit can evolve). Your best bet is to read up on how Social Security works to position yourself to collect as much money from it as possible.