There's a good chance Social Security will be important to you during retirement. After all, 21% of married couples and about 45% of unmarried seniors today depend on Social Security to provide 90% or more of their income. That's why it pays to read up on how the program works and familiarize yourself with some of its lesser-known rules. Here are a few that you may not have known about.

1. You can collect benefits even if you never worked

Even if you never earned an income, if you are or were married to someone who's entitled to Social Security benefits in retirement, you can collect some money as well. It's a provision known as spousal benefits, and it entitles you to up to 50% of your current or former spouse's benefit at full retirement age. Now one thing you should know about spousal benefits is that if you're still married, you can't claim them before your spouse actually files for Social Security. If you're no longer married and have been divorced for at least two years, you can claim spousal benefits even if your ex-spouse hasn't filed yet -- but you must be at least 62.

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2. You get one do-over in your lifetime

The earliest age you can claim Social Security is 62, but filing at that point, or at any age prior to your full retirement age, will result in an automatic reduction in your benefits that will remain in effect for the rest of your life -- unless, of course, you decide to give yourself a do-over. The Social Security Administration will allow you to withdraw your benefits application one time only and file again at a later point. The catch, however, is that you'll also be required to pay back all of the money you collected in benefits to get that second chance. If it's all gone, and that's not possible, then you'll be stuck with the initial monthly benefit you lock in.

3. You'll risk having your benefits garnished if you're behind on taxes

Filing for Social Security early isn't the only way to slash your benefits. If you don't pay your taxes, you'll lose out on some of that income as well. The IRS is allowed to garnish up to 15% of your Social Security benefits to fulfill an outstanding tax debt. The agency won't do that, however, if you reach out and get on a payment plan to fulfill an obligation you can't cover in one fell swoop, so if you find that you owe the IRS money, don't just ignore the problem -- explore your options.

The more you learn about Social Security, the better equipped you'll be to not only file for benefits at the right time, but make strategic moves in advance of retirement that result in a higher monthly payout. Even if you're years away from claiming benefits, it's never too soon to educate yourself about Social Security. And if you're nearing retirement, it's imperative that you get schooled to avoid a mistake that could slash your benefits for life.