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Receiving a monthly Social Security benefit is something plenty of retirees count on. Unless they can't. By the Social Security Administration's estimates, 48 percent of married couples and 69 percent of unmarried individuals get half or more of their income from Social Security. For about 1 in 5 couples, and 44 percent of single people, Social Security represents 90 percent or more of their income.

But 3 percent of people age 60 to 89 are what the government calls "never beneficiaries" who, true to that term, never receive Social Security. And others may encounter circumstances that reduce, suspend or eliminate their benefit. Here's who can't always count on a Social Security safety net:

Non-covered workers

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Roughly 11 percent of those "never beneficiaries" are employees who worked in jobs that receive a public pension and don't pay into Social Security. Among the groups potentially affected: government workers, teachers and railroad employees. (For example, a 2014 report from advocate TeacherPensions.org estimated 1.2 million teachers — or about 40 percent of the nation's public K-12 teachers — aren't covered by Social Security.) Navigating this area of Social Security gets tricky, said certified financial planner Mark LaSpisa, president of Vermillion Financial Advisors in South Barrington, Illinois. You could be eligible for some benefits if your work record includes time at other jobs that did pay into Social Security — but different provisions may kick in that reduce your own benefit by up to 50 percent, or even completely wipe out spousal or survivor benefits. Don't expect a straightforward answer, said LaSpisa, who once spent two years helping a client determine her eligibility for Social Security based on the record of her deceased husband, who had worked for a railroad. "Most of the [Social Security] offices have no clue how to handle this, because it's not a normal process," he said.

Felons

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In many cases, a criminal record doesn't preclude someone from receiving Social Security benefits. But there are a number of exceptions that can limit eligibility in select circumstances. For example, Social Security rules generally prevent someone convicted of the "felonious and intentional homicide" of a worker from receiving benefits based on that deceased individual's record. In other words, killing your spouse makes you ineligible to claim a survival or spousal Social Security benefit on his or her record. Social Security benefits are also typically suspended for otherwise eligible individuals who are currently incarcerated, once they have been confined for 30 days. "Your benefits can be reinstated starting with the month following the month of your release," according to the government.

Delinquent debtors

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Heading into retirement with debt could be a recipe for disaster, if you can't keep up with your obligations. The Department of the Treasury can withhold a portion of your Social Security benefit to collect on delinquent legal obligations such as child support or alimony, as well as tax debts and other non-tax debts owed to a federal agency (think: federal student loans). "No matter what kind of financial trouble you get in, student loans don't really disappear," said Victoria Fillet, a certified financial planner with Roosevelt Investment Group in New York. How much can be taken depends on the details of your debt, but the cap for federal debts is typically around 15 percent of your monthly benefit. The government isn't shy about wielding that power. In fiscal year 2018, collections from consumers' Social Security benefits to cover Department of Education debts totaled $191.5 million; for unpaid federal tax debts, more than $384.9 million, according to data from the Department of the Treasury.

Expats

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Moving overseas for retirement can be a smart financial strategy — and one that generally won't affect your Social Security payments. Many overseas banks accept direct deposit of Social Security checks. But retirees bound for a few specific locations may not be able to receive their benefits. "The U.S. Department of the Treasury prohibits making payments to persons residing in Cuba or North Korea," according to the Social Security Administration. "If you are a U.S. citizen residing in Cuba or North Korea, you can get all the payments we withhold once you move to a country where we can send payments." The Social Security Administration also restricts payments to U.S. citizens who retire to nine other locales — Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Moldova, Tajikistan, Turkmenistan, Ukraine and Uzbekistan — are also be unable to receive benefits, unless they successfully apply for an exception through the Social Security Administration and agree to restricted payment conditions.

Infrequent workers

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