A 501(c)(3) is a U.S. tax-exempt non-profit organization, recognized by the IRS as charitable, religious, educational, or scientific in purpose. The status unlocks two things at once: the organization doesn't pay federal income tax on mission-related revenue, and donors can deduct their gifts on personal or corporate tax returns. A fiscal sponsor is an existing 501(c)(3) that lets a project, initiative, or pre-incorporation effort receive tax-deductible donations and most foundation under its umbrella, without the project itself having 501(c)(3) status yet.
You incorporate as a non-profit corporation in your state, adopt bylaws and a board, then file IRS Form 1023 (or the streamlined 1023-EZ if eligible) requesting 501(c)(3) recognition. The IRS reviews the application and, if approved, issues a determination letter that retroactively applies to the date of incorporation. From that point on, the organization can issue tax-receipt acknowledgments to donors, apply to most foundation grant programs, and access discounts and benefits keyed to non-profit status (Google Workspace for Nonprofits, AWS Imagine grants, sales-tax exemptions in many states).
Form 1023 is non-trivial. The full version takes months and costs a few thousand dollars in legal and filing fees, and the 1023-EZ has revenue limits ($50K projected gross for three years, total assets under $250K). Many projects need to fundraise before they can justify the lift. Fiscal sponsorship solves the timing gap: a project signs an agreement with an established 501(c)(3) that takes a fee (usually 5–10% of funds raised) in exchange for letting the project operate under its tax-exempt status, accept tax-deductible donations, and apply for grants that require 501(c)(3) status.
Comprehensive (Model A) sponsorship folds the project into the sponsor as an internal program. The project's staff are sponsor employees, and the sponsor is legally on the hook. Pre-approved-grant (Model C) sponsorship is more arms-length. The sponsor regrants funds to the project as an independent organization, with the sponsor exercising oversight to make sure the funds are used charitably. Most movement-style projects use Model A; established initiatives that intend to spin out later use Model C.
Apply for your own 501(c)(3) when the work is clearly a long-term independent organization with a board ready to govern it and a budget that can support compliance. Use fiscal sponsorship when you're testing the model, when speed-to-funding matters more than independence, or when the project is genuinely an extension of an existing organization's mission. Many groups start sponsored and graduate to independent status once they cross $250K–$500K in annual revenue.