To verify an organization is truly a 501(c)3 Non-Profit organization you can use one of the following resources.
The IRS. IRS Search for Charities
Publication 78, Cumulative List of Organizations described in Section 170(c) of the Internal Revenue Code of 1986, is a listing of organizations eligible to receive tax-deductible charitable contributions.
GuideStar. GuideStar Non-Profit Reports and Forms
GuideStar gathers and publicizes information about nonprofit organizations.
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