New to Social Security? 2 Rules That Could Catch You Off Guard.

When you first start collecting Social Security, those monthly checks can seem like a financial lifeline. And if you're in the enviable position of having plenty of savings, your Social Security checks could serve as a nice source of extra income, allowing you to do the things you've always wanted.

But if you're new to Social Security and don't know the rules, some of the program's nuances could catch you off guard. Here are two rules you may not be aware of but definitely need to know about.

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1. There's an earnings test for some beneficiaries

You're allowed to work while receiving Social Security checks. Once you reach full retirement age, which is 67 if you were born in or after 1960, you can earn any amount of money from a job without having benefits withheld.

If you work and collect Social Security prior to reaching full retirement age, you'll be subject to an earnings test. And while the limit changes every year, the gist of it is that making too much money could mean having benefits withheld.

This year, for example, if you won't reach full retirement age by Dec. 31, you'll have $1 in Social Security benefits withheld per $2 of earnings above $24,480. This doesn't mean you'll lose the money forever. Once you do reach full retirement age, your benefits should be recalculated and boosted to account for those withheld payments.

Still, in the near term, having benefits withheld could sting, not to mention throw your budget out of whack. So it's important to know that Social Security's earnings test exists, and to familiarize yourself with the limit if you haven't reached full retirement age.

2. Social Security benefits can be taxed

Many Social Security recipients assume that their benefits won't be subject to taxes. But while that's true for some people, it's not a given.

Social Security benefits are taxed based on provisional income, which is the sum of your adjusted gross income, tax-exempt interest income, and 50% of your annual benefit. Once provisional income reaches $25,000 as a single tax filer or $32,000 as a married couple filing jointly, some Social Security benefits could be taxed. Knowing this up front could help you avoid a nasty surprise.

Social Security is a complex program. And if you've only recently started getting benefits, you may not know all the rules. But it's important to learn the program's ins and outs to make the most of those benefits while avoiding financial stress.

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