The Public Support Test

Whether an organisation qualifies as a public charity or must accept private foundation classification comes down to arithmetic — specifically, a fraction calculated across a five-year rolling window that the IRS calls the public support test.

Two versions of the test exist, one for organisations described under IRC § 509(a)(1) — typically churches, schools, hospitals and organisations that solicit broadly from the public — and one for § 509(a)(2), which covers organisations whose income comes substantially from fees and program revenue. Most grant-funded and donation-supported nonprofits fall under the first.

Under § 509(a)(1), the organisation must show that public support amounts to at least one-third of total support over the five-year period ending with the current tax year. Public support means contributions from governmental units, from other public charities, and from the general public — but large individual gifts are capped. Any single donor's contribution counts only up to two percent of total support for the period. This cap is the mechanical heart of the test: it prevents one wealthy patron from artificially inflating the public support fraction. Fees, investment income and unusual grants count as total support but not public support, pulling the denominator up without helping the numerator.

An organisation that falls between one-third and ten percent may still qualify under a facts-and-circumstances test, which considers whether the organisation actively solicits a broad donor base, maintains a governing board representative of the community, and operates programs that serve the public rather than a narrow class.

Falling below ten percent leaves no room for the facts-and-circumstances argument. The organisation is a private foundation, and the consequences are substantial: a two percent excise tax on net investment income, mandatory minimum distributions, restrictions on self-dealing and excess business holdings, and a Form 990-PF filing obligation that discloses every grant made.

The five-year window is calculated on Schedule A of the Form 990 ↗. Because the window rolls forward each year, an organisation's classification can shift — a large one-time gift from a single donor, capped at two percent, may depress the fraction in the years it dominates total support, while its effect dissipates as it ages out of the window. Finance staff who track major gift acknowledgments only for donor relations purposes often miss this dimension: every large gift is also a data point in an ongoing mathematical test with real regulatory consequences.

New organisations are treated as publicly supported during their first five years without having to demonstrate the fraction, giving them time to build a diverse donor base before the arithmetic begins.