Both types of entities must register with the federal government, but a not-for-profit must file more extensive paperwork to earn its tax-exempt status.

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It was incorporated as an Illinois not-for-profit corporation in 1963 at the behest of the ABA, which is a tax-exempt business league.

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Tax-exempt organizations which make money this way are supposed to turn the profit over to the government.

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The idea behind the IRS' campaign is that nonprofits should provide a "community benefit" (say, more free charity care) and not behave like their for-profit counterparts if they want to keep their tax-exempt status.

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The profit on house sales can also be exempt from capital-gains tax.

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