Research participant payments on a B-2 visa: why Form 8233 doesn't apply

A clinical research coordinator walks into the tax office: "I need to pay a research participant from Nigeria $3,000. She's coming in next week on a B-2 visitor visa. Can you process this?"

At most universities, this question triggers a 45-minute conversation that resolves nothing. The tax office reflexively asks for a Form 8233. The international office flags the B-2 visa because visitors can't legally work in the US. The coordinator is left stuck because the protocol requires the payment to clear IRB and the participant is flying in on Monday.

Everyone is wrong in a different way. The participant can be paid legally on a B-2. Form 8233 does not apply. And the $3,000 is fully reportable on Form 1042-S even though it's below the $600 1099 threshold. Let's walk through why.

The scenario

Meet Dr. Amina Okonkwo, a Nigerian physician. Amina is traveling to the US for the first time to participate in a 5-day inpatient clinical trial at a major academic health center. Her role is that of a research subject — not a researcher, not a consultant, not a speaker. She is the object of the research, not the provider of services.

The payment structure is typical for a clinical trial:

• $500 screening visit fee
• $2,500 inpatient participation fee (5 days × $500/day)
• Total: $3,000

Amina has a B-2 visitor visa. She has no US taxpayer identification number. Nigeria has no income tax treaty with the United States. The university has an IRB protocol in place that authorizes the payment.

Three questions need clean answers:

1. Is paying Amina on a B-2 visa legal?
2. What tax form is required from her before the payment?
3. How is the payment withheld and reported?

Question 1: Can you pay someone on a B-2 visa?

This is the question that causes the most confusion. The instinctive answer — "No, B-2 visitors can't work in the US" — is correct but incomplete. It's true that B-2 visitors cannot perform services or engage in employment in the United States. 8 CFR §214.1 and the B-2 visa classification make this unambiguous.

But research participation is not services. A clinical trial subject is not performing labor for the institution. They are allowing the institution to study them. The IRS and USCIS have consistently treated research subject compensation as not services income, and B-2 visa holders are explicitly permitted to participate in activities that do not constitute employment — including clinical research participation.

This is the single most common source of friction between university research administration and tax compliance offices, and it almost always resolves in the participant's favor — but only if the tax office knows the rule.

Question 2: Is Form 8233 required?

Form 8233 is the form a nonresident alien uses to claim a tax treaty exemption on compensation for personal services. The form's official title is Exemption From Withholding on Compensation for Independent (and Certain Dependent) Personal Services of a Nonresident Alien Individual. It applies to services income. Full stop.

Research participant payments are not services income. They are "other income" — specifically, they are treated as miscellaneous income under IRC §61 and reported on Form 1042-S under income code 23 (other income) when paid to a nonresident alien.

This means several things:

• Form 8233 should not be requested from the participant. Requesting it is asking for the wrong form.
• The participant does not need to claim a treaty exemption via 8233 even if a treaty exists (it doesn't for Nigeria, but even for a treaty country, the path would be a W-8BEN claim, not an 8233).
• The absence of Form 8233 is not a reason to withhold at the higher backup withholding rate.

Many university tax offices have a hardcoded checklist that requires Form 8233 for any foreign payment. When the checklist hits a research participant case, the workflow stalls because the form doesn't exist and can't be legally signed. The fix is to recognize that the entire 8233 branch of the checklist doesn't apply to research subjects.

Question 3: Withholding and reporting

Here's where the mechanics get precise. For Amina:

Withholding rate. Default NRA withholding under IRC §1441 is 30% on US-source fixed, determinable, annual or periodical (FDAP) income paid to a nonresident alien. Research participant payments are US-source FDAP income because the activity took place in the United States. Nigeria has no US tax treaty, so there is no treaty-based reduction. 30% applies.

30% of $3,000 is $900. The net payment to Amina is $2,100. The $900 is remitted to the IRS via Form 1042 at year-end.

Reporting form. Form 1042-S, not Form 1099. Here's the critical point many tax offices miss: Form 1099 has a $600 de minimis threshold. Form 1042-S does not. A $3,000 payment is comfortably above the 1099 threshold, so the question usually doesn't come up — but consider a $250 screening fee paid to a foreign participant. That $250 would not generate a 1099 at all. It must still generate a 1042-S. Every dollar of US-source income paid to a nonresident alien is reportable on 1042-S, regardless of amount.

Income code. Use income code 23 (other income) on Form 1042-S. This is the code the IRS reserves for payments that are neither wages, nor services, nor scholarships, nor any other specifically enumerated category. Research participant payments fit here.

Chapter 3 exemption code. Since no treaty applies (Nigeria), use exemption code 00 (no exemption). The full 30% is withheld.

Withholding agent information. The university's withholding agent EIN, legal name, and Chapter 3 status should appear in the header of the 1042-S.

What if the participant is from a treaty country?

If Amina were from a treaty country with a general "other income" article (many US treaties include one, often in Article 21 or 22), the treaty might reduce or eliminate the 30% rate on her research participant payment. The mechanism is not Form 8233 — it is a properly executed Form W-8BEN with the treaty claim in Part II.

Treaties with broad "other income" articles include Canada, the UK, Germany, France, and Japan, among others. The specific rate varies by treaty and by income type. For a participant from Germany, for example, other income paid by a US source is generally taxable only in Germany under Article 21 of the US-Germany treaty, resulting in 0% US withholding.

For a treaty participant, the workflow is:

1. Collect a signed W-8BEN with the treaty claim
2. Verify the treaty article exists and applies to "other income"
3. Apply the reduced (often 0%) withholding rate
4. Report on 1042-S with income code 23 and the appropriate exemption code (04 for treaty)

Still no Form 8233.

Documentation and audit trail

For audit purposes, attach the following to the participant's payment file:

• The IRB protocol number and approval letter
• The consent form signed by the participant
• The participant's W-8BEN (required for any NRA payment, regardless of treaty status)
• A memo explaining the classification as non-services income under income code 23
• The applicable treaty article and page of Pub 515 / Pub 901 if a treaty reduces the rate

The memo is the single most important piece. If the IRS audits your 1042-S filings and asks why you used income code 23 instead of 19 (compensation) or 20 (teaching), the memo is your answer. Without it, you are defending a judgment call from memory.

The summary

Research participant payments on a B-2 visa are one of the cleanest cases in NRA tax compliance once you know the rules — and one of the most frequent sources of friction when you don't. The full picture:

• B-2 visa is legal for research subject participation
• Form 8233 does not apply (it's for services income only)
• Form 1042-S is required, with no de minimis threshold
• Income code 23, exemption code 00 (or 04 if a treaty applies)
• Default 30% withholding unless a treaty "other income" article applies
• Full audit trail tied to the IRB protocol