Your nonprofit just had its best year ever. One generous supporter, someone who truly believes in your mission, gave $80,000. Every other donor combined brought in $12,000. You pop the champagne and start writing thank-you notes.
Your accountant looks at the same numbers and frowns. She sees something you don't: your revenue structure just tilted. If the next few years look the same, your organization could lose its current tax category, along with everything that comes with it for donors, grants, and reputation. Your best year and your biggest risk turned out to be the exact same number.
This lesson is about the test the IRS uses to catch exactly that tilt. It's the most formula-heavy lesson in this course, and we're going to walk through the whole thing: what counts, how it's calculated, and what to do about it. One number, calculated once a year, saves you from an entire category of unpleasant surprises.
The public support test checks that your organization is backed by a broad base of people, not one wallet. For most organizations, the threshold is one third of income from public sources over a rolling five-year window, and any single donor's gift only counts toward that third up to a cap of 2 percent of total support over the same window.
Your public charity status rests on the idea that the public supports you, not a narrow circle. Inside the 501(c)(3) world there's a lesser-known sibling category: a private foundation, an organization that runs on money from a small group of people. Living under private foundation rules is noticeably harder: mandatory annual payout, an excise tax on investment income, and less favorable terms for donors. Your determination letter names your category directly, and for most public charities that's 509(a)(1), the category for organizations that live on donations.
The public support test is an annual check that you still fit your category. The rule for 509(a)(1): at least one third of your support needs to come from public sources. This isn't measured over a single year, it's measured over a rolling five-year window, this year plus the four before it. The five-year window works like a built-in grace period: one strange year doesn't wreck the whole picture, what matters is the trend.
Two built-in cushions worth knowing from the start. New organizations don't have to pass the test for their first five years, it kicks in for real starting year six, though the numbers from those early years still feed into your first five-year window once it starts. And if your percentage falls below a third but stays above 10 percent, there's a backup option called the facts and circumstances test: you show the IRS that, taken as a whole, you're still operating like a public organization, running ongoing fundraising, drawing support from a wide circle. It's a subjective judgment call with no guarantees, a fallback, not a second home. Below 10 percent, there's no fallback left.
The formula on its surface is simple: public support divided by total support, both measured over five years. The whole trick is in what counts as public support.
Almost everything goes into the denominator: donations, grants, contributions, investment income. Donations and grants go into the numerator too, but with an important limit. One person's giving only counts as public support up to 2 percent of your total support over five years. Anything they give above that still sits in the denominator, but it drops out of the numerator entirely.
Let's go back to the story that opened this lesson and run the numbers. Say you raised $120,000 total over five years, and $80,000 of that came from one person. Their cap: 2 percent of $120,000, which is $2,400. Out of their $80,000, only that $2,400 counts toward the numerator. Public support: $12,000 from everyone else plus $2,400, for a total of $14,400 out of $120,000, exactly 12 percent. The organization having the best year in its history just landed in fallback territory, a few steps from the edge. That's what your accountant saw.
One important exception to the cap. Money from government sources and from other public charities isn't capped at all, it goes into the numerator in full. That's why an $80,000 government grant and an $80,000 gift from a private individual look completely different to this test, even though they're identical on your bank statement.
If your category is 509(a)(2), meaning you live mostly on income from your own programs, the formula is similar but not identical, and there's no 10 percent fallback available. Check the specifics for your category with your CPA.
Calculate once a year. Set aside an evening with the calculator below, since you'll need the same math for Schedule A of your Form 990 anyway. Knowing your percentage before you file beats finding out from the filing itself.
Know your zone. Well above a third: relax, keep supporting a diverse mix of sources. Right around a third: pay attention, run the math on every large gift ahead of time. Between 10 and 33: time for a conversation with your CPA and a plan to climb back above a third. Below 10: that conversation doesn't wait.
Treat diversity as protection for your status, not just for your stability. Everything this course builds around fundraising, many small donors, recurring gifts, government grants, works double duty here. A hundred people giving $200 each contributes more to your numerator than one person giving $20,000, for identical dollars in the bank.
And one last thing, so nothing here gets misread: large gifts aren't the enemy, don't turn them away. What's dangerous isn't the gift, it's not seeing its effect on your structure. A large gift on top of a healthy, broad base is cause for celebration. A large gift instead of a broad base is the number your accountant frowns at.
Run your numbers through the calculator above and write the result down on one page: your percentage, your zone, your three largest donors and their contribution to the picture, the date you calculated it. Update this every year before you file your 990. If you land below the comfortable zone, add a second page: a diversification plan, worked out with your CPA.
What happens if I fail the test once?
Nothing catastrophic right away: the IRS looks at the five-year window and the trend. But it's a clear signal to address your revenue structure without waiting.
Do grants from foundations count the same way as gifts from individuals?
Yes, grants from private foundations fall under the same 2 percent cap as gifts from individuals. Government grants and grants from other public charities aren't subject to that cap.
Do I need to calculate this if my organization is only two years old?
The test officially starts in year six, but calculating early is still worth it: you'll see the trend before it becomes a problem.
The test that looked like a threat at the start of this lesson actually just measures something you already want to build: an organization backed by many people, not one wallet. The formula turns that goal into a number and reminds you to check it once a year.
Next up: another quiet topic, income you earn yourself, and a tax most people only find out about after the fact. Let's get ahead of it.
The material in this lesson is educational and drafted for review by your attorney and CPA. This course does not replace professional advice and makes no promise of outcomes.