Social Security provides income to millions of retired seniors today, and chances are, you'll depend on it once your career comes to an end. The more you know about how the program works, the easier it'll be for you to make the most of it. With that in mind, here are a few key facts about Social Security it pays to be aware of.

1. You can undo your benefits if you file too early

Though you're allowed to start collecting Social Security once you turn 62, you can't claim the full monthly benefit you're entitled to based on your earnings history until you reach full retirement age. Full retirement age isn't a universal age; it depends on your year of birth, and it's either 66, 67, or somewhere in between. For each month you file for benefits ahead of your full retirement age, they'll be reduced on a permanent basis -- that is, unless you manage to undo your claim.

Five Social Security cards spread out against blue background

IMAGE SOURCE: GETTY IMAGES.

The Social Security Administration (SSA) lets you undo your filing once in your lifetime, which means that if you claim benefits early and regret that decision after the fact, you get a year to withdraw your application and repay the SSA every dollar it paid you. As long as you manage to do these two things, you'll get the option to file again at a later point in time -- ideally, at full retirement age, or even beyond, which means you won't face a lifetime reduction in your monthly income.

2. You can collect benefits even if you didn't work

Social Security benefits are based on workers' earnings histories -- specifically, their top 35 years of wages. That said, you need to earn a certain number of work credits in your lifetime to be eligible to collect benefits of your own. You can earn a maximum of four credits annually, and the earnings amount associated with each credit varies from year to year. In 2019, for example, workers receive one credit per $1,360 of income. But overall, you need to put in at least 10 years in the workforce to qualify for benefits on your own earnings record.

That said, there's still a way to claim benefits in retirement even if you never worked a day in your life. If you're married to someone who's eligible for Social Security, or are divorced from someone who gets benefits, you're entitled to spousal benefits equal to up to 50% of your spouse's (or former spouse's) benefit at full retirement age. This means that if your spouse is entitled to $1,600, you get to collect $800, despite your absent work history.

3. Your benefits may be subject to taxes

Seniors are often surprised to learn that much of their income is subject to taxes. And unfortunately, Social Security falls into this category. Whether you'll pay taxes on your benefits, however, depends on how much total annual income you have, and the state you retire to.

If your provisional income -- non-Social Security income plus 50% of your yearly benefits -- is between $25,000 and $34,000 as a single tax filer, or between $32,000 and $44,000 and as a joint tax filer, you could face taxes on up to 50% of your benefits. And if your provisional income exceeds $34,000 as a single tax filer, or $44,000 as a joint filer, then you could be liable for taxes on up to 80% of your benefits.

In addition, there are 13 states that tax benefits to varying degrees: Colorado, Connecticut, Kansas, Minnesota, Missouri, Montana, Nebraska, New Mexico, North Dakota, Rhode Island, Utah, Vermont, and West Virginia. If you live in one these states, you may be on the hook for taxes, though most offer an exemption for low-to-middle earners that could ease that burden. Minnesota, North Dakota, Vermont, and West Virginia are the only ones that don't offer an exemption, so prepare to lose some of your Social Security income to taxes if you reside in one of those four states.

It's important to get educated on Social Security's ins and outs so you're well-equipped to maximize your benefits once you're eligible to claim them. Keep these lesser-known points about the program in mind, as they could help in the course of your retirement planning.