The U.S. allows its citizens to have more than one passport, but often there isn’t any tax advantage to doing so, tax experts say.

“No matter how many citizenships they hold, Americans still owe U.S. taxes on their world-wide income,” says Philip Hodgen, an international tax lawyer who practices in Pasadena, Calif.

There is a more extreme, and permanent, maneuver: renouncing U.S. citizenship outright. People considering that should be aware that the process can be long, complex and costly, tax experts say. Here are some issues to be aware of.

Tax-Compliant

Renouncers must certify that they have been tax-compliant for the last five years—and sometimes produce the returns to prove it. For this reason, renouncing citizenship isn’t a ready solution for coping with past tax errors, tax experts say.

Exit Tax

Some would-be expatriates owe a hefty exit tax. The law treats many renouncers as having sold all their world-wide assets on the day before the renunciation, even if the person will continue to own the property and pay tax on it.