Blog · 15 October 2026

Charitable Bunching and Donor-Advised Funds Under OBBBA’s 0.5% AGI Floor: What US CPA Firms Should Tell Clients

By Keshav Bansal, CA

From tax year 2026, itemizers face a new 0.5% AGI floor on charitable deductions under the One, Big, Beautiful Bill Act (OBBBA). That is why charitable bunching with a donor-advised fund is back on planning checklists for US CPA firms. Vanguard Charitable (Sept. 30, 2026) walked through the math: a couple with $700,000 of AGI who give about $40,000 a year lose $3,500 to the floor every year; contributing $120,000 once to a DAF absorbs that floor a single time and still supports the same long-term giving plan.

What the 0.5% AGI floor does

IRC §170(b)(1)(I), as amended by OBBBA, allows itemized charitable contributions only to the extent the aggregate exceeds 0.5% of the taxpayer’s contribution base for the year. Contribution base is essentially AGI computed without regard to any net operating loss carryback. The floor applies to cash and noncash gifts. Amounts that fall under the floor generally do not carry forward; they are simply lost for that year. The familiar percentage-of-AGI caps still apply after the floor—typically up to 60% of AGI for cash to public charities and 30% for long-term appreciated property to public charities, with a five-year carryforward of amounts limited by those caps.

Practitioner summaries (including CASE’s FAQ on OBBBA’s charitable provisions) treat the floor as taking effect for tax years beginning in 2026. It applies only to itemizers. Non-itemizers use a different rule, described below.

Why annual giving gets expensive under the floor

The floor is annual. A client who itemizes and gives every year pays the 0.5% “toll” every year. Using Vanguard Charitable’s illustration: at $700,000 AGI, 0.5% is $3,500. Three years of $40,000 gifts mean three $3,500 bites—$10,500 never deducted—before percentage limits. One $120,000 contribution in a single year means one $3,500 bite, so more of the same total giving becomes deductible. Northern Trust and similar advisors make the same point: consolidating giving into fewer years reduces how many times the floor applies, while a DAF or private foundation can hold pre-funded gifts for later grants to operating charities.

How a donor-advised fund supports bunching

A donor-advised fund is an account at a sponsoring public charity. The donor contributes cash or appreciated stock, generally takes the charitable deduction in the contribution year (subject to §170 rules, including the new floor and AGI caps), and later recommends grants to eligible charities. The sponsor has exclusive legal control of the assets; the donor’s role is advisory. For substantiation of DAF gifts and other §170 paperwork, see our guide to charitable contribution substantiation after Williams.

Bunching into a DAF lets the client clear the 0.5% floor once while spreading cash support to favorite causes over several years. Appreciated long-term stock contributed to a public-charity DAF can still avoid recognizing capital gain on the donated shares, subject to the usual basis and holding-period rules—and still faces the 0.5% floor and the 30%-of-AGI property limitation in the contribution year.

The non-itemizer cash deduction—and why DAFs do not qualify

IRS Topic no. 506 (reviewed/updated Sept. 24, 2026) confirms that beginning with tax year 2026, taxpayers who do not itemize may deduct up to $1,000 ($2,000 if filing jointly) of cash contributions to certain qualified organizations. That break is separate from Schedule A and is not subject to the itemizer 0.5% floor.

Gifts to donor-advised funds do not qualify for that above-the-line (non-itemizer) cash deduction. CASE’s OBBBA FAQ and other practitioner write-ups are clear: the non-itemizer provision is limited to cash gifts to eligible public charities and excludes DAFs, supporting organizations, and private foundations. Clients who take the standard deduction and want the $1,000/$2,000 break need to give cash directly to an eligible charity—not through a DAF.

Related tools that are not the same as bunching

Qualified charitable distributions (QCDs) from an IRA remain a different strategy for clients age 70½ or older. QCDs are excluded from AGI when done correctly; they are not Schedule A deductions and do not use a DAF. Donor-advised funds do not qualify for QCDs. See our QCD and Form 1099-R Code Y guide. Charitable remainder annuity trusts and other split-interest vehicles are also outside this post’s scope; listed-transaction rules for certain CRAT promotions are covered separately.

OBBBA also affects withholding and other 1040 planning. When clients change how they itemize or bunch gifts, revisit projected taxable income and withholding—our draft 2027 Form W-4 / OBBBA overview is a useful companion.

CPA checklist for 2026 giving conversations

1. Model the floor. Compute 0.5% of projected contribution base for each year the client expects to itemize and show dollars lost if giving stays level every year.
2. Compare annual vs bunched. Run a multi-year projection: same total gifts spread yearly versus one larger year (often into a DAF), after the floor and after 60%/30% AGI caps.
3. Separate itemizers from non-itemizers. Non-itemizers should not route the $1,000/$2,000 cash deduction through a DAF; point them to direct cash gifts to eligible charities per Topic 506 and OBBBA’s eligibility rules.
4. Watch stock gifts. Appreciated property still has basis, holding-period, and Form 8283/appraisal issues; the floor applies to those gifts too.
5. Document the DAF gift. Keep bank records and the contemporaneous written acknowledgment from the sponsoring organization; §170(f)(18) also requires that the sponsor have exclusive legal control.
6. Do not confuse carryforwards. Excess over percentage caps can carry forward up to five years; amounts lost to the 0.5% floor generally cannot.
7. Coordinate retirement giving. For IRA owners who want AGI exclusion, evaluate QCDs separately from DAF bunching.

Where Tax Brew fits

Year-end charitable modeling stacks onto an already busy 1040 calendar. Tax Brew supports US CPA firms with tax prep support, bookkeeping and cleanup so reviewers can spend more time on judgment calls like bunching versus annual giving. See our services, or email info@taxbrewglobal.com.

Sources: IRC §170(b)(1)(I) (0.5-percent floor); IRS Topic no. 506, Charitable contributions (reviewed/updated Sept. 24, 2026); CASE, FAQ: Charitable Giving Provisions in the OBBBA; Vanguard Charitable (Sept. 30, 2026) bunching example; practitioner summaries on OBBBA charitable rules (including CCH). This article is general information, not tax advice for any specific client.