Orphan Drug Credit vs R&D Credit: Clinical Trials

The orphan drug credit under IRC §45C equals 25% of qualified clinical testing expenses for a drug the FDA has designated for a rare disease, counting only testing after the designation date and before approval. It counts payments to contract research organizations at 100% and has no base amount. The R&D credit under IRC §41 covers far more work, including trials for any indication, but it is incremental and counts contract research at 65%. The same expenses cannot earn both credits in the same year. And for a pre-revenue company, only the §41 credit can be used against payroll taxes.

Which credit is better depends on your designation dates, your CRO contracts and whether you owe income tax. Here is how the two fit together.

How the §45C orphan drug credit works

The mechanics come almost entirely from the statute:

Rate. 25% of qualified clinical testing expenses for the year (§45C(a)). The Tax Cuts and Jobs Act cut it from 50% to 25% for tax years beginning after December 31, 2017. Nothing since has changed the rate: as of this writing, §45C still reads 25%, and the 2025 law that created §174A did not amend it.
Qualified clinical testing expenses. Amounts that would be qualified research expenses under §41(b) if “clinical testing” replaced “qualified research,” with 100% of contract payments counted instead of 65% (§45C(b)(1)). That means wages, supplies, computer rental and contract amounts for the testing, not depreciable equipment.
Clinical testing. Human clinical testing carried out under an investigational exemption under section 505(i) of the Federal Food, Drug, and Cosmetic Act, for a drug being tested for a rare disease, conducted by or on behalf of the company that holds the orphan designation (§45C(b)(2)). It counts only to the extent it relates to the designated rare disease.
Rare disease. One that affects fewer than 200,000 people in the United States, or more than that where there is no reasonable expectation of recovering U.S. development costs from U.S. sales (§45C(d)(1)).
Funded amounts are out. Expenses funded by a grant, contract or another person, including a government entity, are excluded (§45C(b)(1)(C)).
Foreign testing is mostly out. Testing outside the United States counts only if the U.S. testing population is insufficient and the testing is done by a U.S. person or an unrelated person (§45C(d)(2)).
It is an annual election, claimed on Form 8820 and carried to Form 3800 as a general business credit.

One structural difference matters more than it looks. Because §45C substitutes “clinical testing” for “qualified research,” the question is whether the spending is qualifying human clinical testing of the designated drug, not whether it passes the §41 four-part test. The statute itself contemplates that some qualified clinical testing expenses are not §41 qualified research expenses (§45C(c)(2)).

Designation timing: the date that starts the clock

Only testing after the designation date under section 526 of the FD&C Act, and before approval under section 505(b) (or, for a biologic, licensure under section 351 of the Public Health Service Act), counts toward §45C. Money spent on a trial before designation is not a qualified clinical testing expense, however rare the disease.

FDA rules let a sponsor request orphan designation at any time before it submits a marketing application for the drug for the same rare disease (21 CFR 316.23), and designation can also be requested for an unapproved use of an already approved drug. The practical point is simple: the earlier designation lands, the more trial spend can count. Form 8820 asks for each drug’s name, designation application number and designation date, so keep the FDA letter with your tax records.

How §45C and §41 coordinate

Three rules keep the same dollars from being rewarded twice:

No overlap in the election year. Qualified clinical testing expenses for a year in which you elect §45C are not taken into account for the §41 credit that year (§45C(c)(1)). The Instructions for Form 6765 put it plainly: you can elect to claim the orphan drug credit for these expenses instead of the research credit.
They still count in your §41 base. Any of those expenses that are also qualified research expenses are included in base-period research expenses when you compute §41 in later years (§45C(c)(2)). Moving trial spend to §45C does not lower the base your other research is measured against.
No double deduction. Under §280C(b), your deduction for qualified clinical testing expenses is reduced by the §45C credit, unless you elect a reduced credit. The reduced credit multiplies the credit by one minus the top corporate rate, which is 19.75% of expenses instead of 25% on Form 8820. The election must be made on a timely filed original return, including extensions, and is irrevocable for that year. The TCJA added it in 2017, alongside the rate cut.

The §41 side has its own parallel election under §280C(c); our guide to the §280C election covers it.

CRO payments: 100% under §45C, 65% under §41

For many clinical-stage companies, CRO fees are among the largest costs, and this is where the two credits diverge most.

Under §41, contract research counts at 65% of the amount paid (§41(b)(3)(A)). Treas. Reg. §1.41-2(e) adds three requirements: the agreement is in place before the research, the research is performed on your behalf (you have a right to the results), and you bear the cost even if the research fails. Payments contingent on success are treated as buying a result, not research. Research performed outside the United States is excluded entirely (§41(d)(4)(F)).

Under §45C, contract clinical testing counts at 100%. Because §45C builds on the §41(b) contract definitions, the same contract terms deserve the same scrutiny. The foreign rule is also different: foreign sites can count for §45C in the narrow case above, never for §41. Our pharmaceutical and biotech industry page covers the §41 treatment of CRO geography in more detail.

An illustrative comparison

Take a hypothetical company that pays $1,000,000 in one year to a U.S. CRO for a Phase 2 trial of a drug with orphan designation, all after the designation date and none of it funded by anyone else. Assume the trial is its only research and its qualified research expenses averaged $650,000 over the prior three years.

	§45C orphan drug credit	§41 R&D credit (ASC)
Expense counted	$1,000,000 (100% of CRO cost)	$650,000 (65% of CRO cost)
Base amount	None	$325,000 (50% of the $650,000 prior average)
Credit rate	25%	14% of the excess
Credit before §280C	$250,000	$45,500
Usable against payroll tax?	No	Yes, if a qualified small business elects

Illustrative only - every figure is invented for this example, and a real comparison runs on your whole research base.

On paper §45C wins by a wide margin. The last row is why that is not the end of the analysis.

When §41 is the only option

Plenty of clinical-stage spending never reaches §45C:

Indications without orphan designation.
Testing before the designation date.
Preclinical work - discovery, in vitro and animal studies - which is not human clinical testing.
Formulation, manufacturing process and analytical method development.
Post-approval trials for new indications, dosages or delivery forms, unless the new use has its own orphan designation. For §41, testing that needs a new FDA approval is not treated as research after commercial production (Treas. Reg. §1.41-4(c)(2)(iv)).

For all of these, the §41 credit is the only federal research credit, and whether each activity passes the four-part test is a fact question.

Pre-revenue biotechs: the payroll offset changes the math

A company that owes no income tax cannot use either credit against income tax this year. The difference is what happens instead.

Under §41(h), a qualified small business - gross receipts under $5 million for the year and no gross receipts in any year before the five-year period ending with it - can elect to apply up to $500,000 a year of its §41 credit against employer payroll taxes. The election is made on a timely filed original return, is available for no more than five tax years, and the offset starts in the first calendar quarter beginning after that return is filed, claimed on Form 8974 with Form 941. Our payroll tax offset page walks through the mechanics.

The §45C credit has no payroll option. It is a general business credit: usable against income tax within the general business credit limits, and otherwise carried back one year and forward 20 years (§39). Carryforwards can be limited after an ownership change (§383), which a financing round can trigger.

So a pre-revenue company faces a real trade-off: a smaller §41 credit it can turn into payroll cash now, or a larger §45C credit it may use years later, if ever. The election is annual. In a year you elect §45C, that year’s qualified clinical testing expenses come out of the §41 computation, but your other research - preclinical wages, for example - can still support a §41 credit and a payroll election. Run it both ways every year, with your CPA.

Documentation for either credit

The records that support one credit mostly support the other:

The FDA designation letter, with the application number and date, and the IND under which the trial runs.
Protocols and site lists, including where patients were enrolled, to separate U.S. from foreign testing.
CRO agreements, showing pricing, any success-contingent payments, and who owns the data and results.
Grant and partner funding terms, since funded amounts are excluded under both §41(d)(4)(H) and §45C(b)(1)(C).
Allocations between the designated indication and any others, and between spending before and after the designation date.
Time records for clinical operations, regulatory and biostatistics staff.
Four-part test support for anything claimed under §41, by business component.

FAQ

Can we claim both credits on the same trial?

Not on the same expenses in the same year. In a year you elect §45C, that year’s qualified clinical testing expenses are excluded from the §41 computation, although they still count in your §41 base for later years.

What was the orphan drug credit rate before 2018?

50%. The Tax Cuts and Jobs Act reduced it to 25% for tax years beginning after December 31, 2017, and added the reduced-credit election under §280C(b)(3).

Did the 2025 tax law change the orphan drug credit?

Not its text. §45C still provides a 25% credit. The 2025 law restored immediate expensing of domestic research spending under §174A, which affects the deduction side of the same budget.

Can the orphan drug credit offset payroll taxes?

No. The §41(h) payroll election applies only to the §41 research credit.

For the full picture of how the §41 credit is computed, see calculation methods and the R&D tax credit guide.

Sources

IRC §45C - Clinical testing expenses for certain drugs for rare diseases or conditions, IRC §41, IRC §280C, IRC §39 and IRC §383 (U.S. House, Office of the Law Revision Counsel)
Treas. Reg. §1.41-2 - Qualified research expenses and Treas. Reg. §1.41-4 - Qualified research (eCFR)
21 CFR 316.23 - Timing of requests for orphan-drug designation (eCFR)
IRS - About Form 8820, Orphan Drug Credit, the Instructions for Form 6765 and About Form 8974

Clinical Trials: Orphan Drug Credit vs the R&D Credit