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Older Americans have many reasons for taking on part-time work after leaving a full-time job behind — perhaps better financial security, a sense of purpose or a way to stay connected. It's also becoming more common to work well into one's 60s or 70s, or even 80s. By 2026, about 30% of people ages 65 to 74 are forecast to be working either full or part time, compared with 17.5% in 1996, according to data from the Bureau of Labor Statistics. Among the 70-and-older crowd, that share is projected to reach 10.8% in 2026, more than double what it was 30 years earlier (4.7%). Financial advisors say that if you're among those who are considering a part-time job after putting an end to 40-hour work weeks, it's important to know how the income can impact other things that tend to be particular to older Americans — including your nest egg, Social Security and Medicare.

Your portfolio

If you're unsure whether your retirement savings will truly get you through your older years and part-time work can reduce what you withdraw, advisors say go for it. "For folks where it's on the bubble of whether their retirement plan is going to work, it can be worth it to work — and that doesn't mean full time," said Nick Defenthaler, a certified financial planner with the Center for Financial Planning in Southfield, Michigan. "Part-time work will reduce what you have to take from your overall portfolio." Any amount you earn from a job could reduce (or eliminate) what you need to withdraw from your retirement account. Leaving those assets invested, where they can keep growing and benefit from compound interest, will pay off down the road. "You don't have to make big money," said CFP Matt Rogers, director of financial planning at eMoney Advisor, a financial software firm that works with advisors. "Just having some income to reduce withdrawals is good."

Social Security

If you already have reached your full retirement age (as defined by the government) and are receiving Social Security, you can earn as much as you want without any reduction in your benefits (although up to 85% is subject to federal income taxes, depending on your overall income). If you haven't yet reached that magic age, however, it's a different story. While delaying Social Security for as long as possible means a higher monthly check, many people take it as soon as they can — age 62 — or soon thereafter.

If you start getting those monthly checks early, there's a limit on how much you can earn from working without your benefits being affected. For 2019, that cap is $17,640. Earn more than that and your benefits will be reduced by $1 for every $2 you earn over that threshold. Be aware, too, that the reduction in benefits can come as a surprise — and all at once, said CFP Peggy Sherman, a lead advisor at Briaud Financial Advisors in College Station, Texas. Say you earned $5,000 over the limit in a given year and the Social Security Administration discovers it later when it does its annual review of your tax return. "They don't adjust your benefits just a little bit — they'll stop your benefits until the amount is paid back," Sherman said. "It can be a very ugly surprise." More from Personal Finance:

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What to know before putting money in 'do good' investments Then, when you reach full retirement age around age 66 or 67 — the exact age depends on your birth year — the money comes back to you in the form of a higher monthly check. However, "it can take up to 15 years to recoup that reduction," Sherman said. "They don't give it back all it once. You get a little each month." Also, if you are one of those early takers who is working and you reach full retirement age during 2019, then $1 gets deducted from your benefits for every $3 you earn above $46,920.

Medicare