Millions rely on Social Security to help them make ends meet in retirement. But Social Security is complicated enough that many people never knew about a key strategy that could have given them a lot of flexibility in deciding when to take their Social Security benefits.

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, walks through the little-known strategy. He notes that until late 2010, the withdrawal-of-application strategy allowed Social Security recipients to get a do-over on their choice of when to start taking benefits. Simply by repaying the benefits you received, you could get the right to refile for benefits at a later age, reaping larger monthly benefits in the process. Dan explains that now, though, the rules for withdrawing your application for Social Security benefits are much more restrictive, giving you just one chance and only allowing you to turn back the clock by 12 months. 

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