The Roth IRA is a powerful but frequently misunderstood retirement savings vehicle. If you have a Roth IRA or are considering opening one, it's important to understand the rules that govern their operation -- or you could find yourself liable for rather nasty fees and penalty taxes. Here are some of the most important Roth IRA rules that you may not know.

They share a contribution limit with other IRAs

In 2017, the annual contribution limit for IRAs is $5,500 (plus an additional $1,000 catch-up contribution if you're 50 or older). However, what many people fail to realize is that this limit includes all your contributions to all the different types of IRAs you may own. In other words, you may contribute only $5,500 in total, split between your traditional IRAs and your Roth IRAs. Exceed this contribution limit and you'll be liable for penalty taxes until you fix the excess contribution.

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Roth IRAs have an income cap

Roth IRAs are such a great resource that the IRS put an income limit on who can contribute to one. If your modified AGI is $194,000 or higher (for married filing jointly) or $132,000 (for everyone else), you can't contribute to a Roth IRA that year. If your modified AGI is below these limits but at or above $186,000 (for married filing jointly) or $118,000 (for everyone else), the amount you can contribute is reduced. However, there is a way to get around this limitation, as you'll see in the next section...

There is a "backdoor" option

If your income is too high to allow you to contribute to a Roth IRA normally, you can manage it with the slightly sneaky "backdoor" approach. You see, while there is an income limit for Roth contributions, there's no income limit for Roth conversions (meaning that you convert a traditional IRA to a Roth IRA). All you have to do is open a new traditional IRA, contribute as much as you like up to the annual limit, and then convert the new account into a Roth IRA. If you have no other traditional IRAs and do all this during the same year, you'll owe little to nothing in taxes for the conversion (you would owe income taxes on any returns you made between opening the traditional IRA and turning it into a Roth IRA). However, be aware that if you do have other traditional IRAs, the pro rata rule means that you may have a more significant tax bill. If this is the case, consult with a financial advisor before making your decision to proceed.

Some limitations on traditional IRAs don't apply to Roths

Income limit aside, Roth IRAs are actually burdened with fewer limitations than traditional IRAs are. For example, there are no required minimum distributions from Roth IRAs, you can contribute to a Roth IRA at any age (contributions to traditional IRAs cut off at age 70 1/2), and you can contribute up to the annual maximum to a Roth IRA even if you're covered by an employer-sponsored retirement plan. You can even take money out of the account tax-free before you hit retirement age; if you only take out money you contributed five years or more ago, you won't have to pay income taxes or penalties on the distribution.

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