There's a deeply ingrained irony in the Social Security system. That is, while benefits from the social safety net were never intended to be a retiree's sole source of income, they're nevertheless reduced in certain instances if you earn money from other sources.

The good news is that this reduction only affects a small and temporary segment of Social Security beneficiaries. That is, if you work at or after your full retirement age (aged 66 for people born between 1943 and 1960, and aged 67 for those born since 1960), then your benefits won't be reduced. On the other hand, they are negatively affected if you elect to receive Social Security and work before reaching the full retirement threshold.

To discover how much outside income will affect your benefits, check out the following video, in which Motley Fool contributor John Maxfield walks viewers through the math that makes this determination.

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