What each control does

1. Jurisdiction: scopes the scenario to one state or nationally. Taxpayers are counted by residence; a taxpayer may give to any participating state’s scholarship granting organization (SGO) regardless of where they live.
2. Percentage who participate: the share of eligible taxpayers who give. Any taxpayer who owes federal income tax is an eligible donor. Under Treasury’s proposed rules, each spouse on a joint return is a separate taxpayer with his or her own $1,700 limit, so a married couple filing jointly counts as two taxpayers and can claim up to $3,400, limited by the couple’s combined tax bill. The rate is applied to all taxpayers equally; controls in the advanced details allow separate assumptions for full-credit and partial-credit taxpayers.
3. Full-credit taxpayers: the share of taxpayers who can claim the full $1,700 and give: those whose simulated 2027 federal income tax bill is at least $1,700, or at least $3,400 for a married couple filing jointly (both spouses then count as full-credit).
4. Partial-credit taxpayers: the share of taxpayers who owe some federal income tax but less than that and give. Their gift is limited by their tax bill; spouses on a joint return that owes less than $3,400 are counted as splitting it evenly.
5. Scenario presets (in Advanced Details): one-click combinations of the two rates: Launch 2% & 0.5%, Growth 5% & 1%, Maturing 8% & 3%, Scale 20% & 20% (full-credit/partial-credit).
6. Calculator giving assumptions: full-credit taxpayers give $1,700 each ($3,400 for a married couple filing jointly) and a representative share of partial-credit taxpayers give their entire tax bill at a given participation rate. As a robustness check, the Affordability Check allows you to cap donations at a % of household income for a scenario where uptake of the individual W-4 giving route is not widespread and so middle-income donors are more constrained in their giving by cashflow / liquidity restrictions (i.e., more difficult to make cash donations to SGOs up front).
7. Scholarships funded: total raised divided by the average scholarship set with the slider in that box ($500 to $10,000; default $5,000; AFC’s October 2026 donor summary used $3,500). It counts every dollar raised; SGOs must spend at least 90 percent of their income on scholarships, so the figure is an upper bound at that award size.

Taxpayers vs. tax filers. This calculator counts taxpayers: each spouse on a joint return is one taxpayer. Tax filers (tax returns) count a married couple filing jointly once, so the 172.0 million eligible taxpayers file 121.5 million tax returns. Treasury’s analysis of the proposed rules projects that more than 11 million taxpayers would give $26 billion a year at 10 percent take-up. That count is close to the 12.2 million tax returns behind this calculator’s 10 percent scenario rather than its 17.2 million taxpayers, while the dollars raised are almost exactly the same: $26.3 billion here vs. Treasury’s $26 billion.

In every scenario, these projections assume tax filers will not give more than their federal income tax liability in the given tax year. A green ✓ marks a state that has signaled intent to or has opted in as of October 2026. Opting in governs where scholarships are funded, not who may donate.

Sources

1. American Federation for Children Growth Fund, Who Can Fund a Scholarship? Updated Donor Estimates Under the New Federal Education Freedom Tax Credit (EFTC) (Sept. 2026), updated Oct. 2026, afcgrowthfund.org/s/AFCGF-Who-Can-Fund-a-Scholarship-EFTC-Eligibility-Report-s5t9.pdf.
2. Donor pool and gifts simulated per filer under enacted 2026–2027 (OBBBA) tax law on U.S. Census ACS microdata, post-stratified to an income-migrated, growth-adjusted projection of the TY2027 IRS filer universe.
3. U.S. Department of the Treasury and Internal Revenue Service, proposed regulations REG-117199-25 (Oct. 2026): proposed § 1.25F-2(a)(2) and Example 2 (each spouse on a joint return is a separate taxpayer for the $1,700 limit); economic analysis (more than 11 million taxpayers giving $26 billion a year at 10 percent take-up).
4. Opt-in roster: 31 states as of October 2026, per AFC’s Federal Scholarships state opt-in tracker, federalscholarships.com.

Illustrative scenarios. Participation rates and the giving-rate assumption are user-set inputs, as is the average scholarship amount; none are AFC estimates or projections. Taxpayer counts and capacity are the certified figures from the AFC donor-capacity analysis, updated for Treasury’s proposed rules; this calculator shows potential fundraising, not a forecast and not a federal revenue estimate.