01 · The Question
If a Participant Leaves Early, Do You Still Have to Pay Them?
A participant agrees to a six-visit study but withdraws after the fourth visit. Do they receive nothing because they did not finish? Four-sixths of the promised amount? Everything?
The answer depends partly on what the payment represents.
Reimbursement for expenses already incurred, compensation for participation already completed, and a genuine bonus specifically offered for completing the study do not serve the same purpose. Treating them as one undifferentiated payment can turn an otherwise straightforward withdrawal into an ethical problem.
03 · What You Need to Know
The Right to Withdraw Changes How Payment Should Be Structured
Participants Have a Right to Stop Participating
Voluntary participation does not end when the consent form is signed. Under the U.S. Common Rule consent requirements, prospective participants must be informed that participation is voluntary and that they may discontinue participation without penalty or loss of benefits to which they are otherwise entitled.
Payment arrangements therefore need to be designed so that they do not improperly penalize a person for exercising that right.
OHRP specifically recommends prorating payment in studies of considerable duration or involving multiple interactions or interventions rather than delaying all payment until completion, because withholding payment until the end could unduly influence a participant's decision about withdrawal. FDA similarly states that payment credit should accrue as the study progresses and should not be contingent on completion of the entire study.
Money Already Accrued Is Different From Money for Future Participation
Suppose a participant has completed four of six scheduled visits. If each completed visit involved time and burden for which compensation was promised, that contribution has already occurred. Withdrawal does not make those four visits disappear.
SACHRP recommends that reimbursement and compensation accrue in proportion to participation. Its reasoning is straightforward: expenses have already been incurred and participants have already contributed their time and accepted the burdens associated with completed activities. Making those payments conditional on finishing the entire study changes their function from reimbursement or compensation into leverage for retention.
Accrued payment
Payment associated with expenses already incurred or time, effort, and burdens already contributed.
Future payment
Payment associated with research activities the participant has not yet completed.
A participant who withdraws ordinarily does not acquire compensation for future visits they never complete. But that is different from forfeiting compensation already accrued.
Reimbursement Should Follow Expenses Already Incurred
Reimbursement is especially clear conceptually. If a participant spent money on approved transportation to attend a completed study visit, later withdrawal does not undo the transportation expense.
SACHRP describes reimbursement as repayment of reasonable out-of-pocket costs arising from participation and recommends that such payments accrue with the costs themselves. Making reimbursement conditional on eventual study completion would convert repayment of actual expenses into an incentive to remain enrolled.
The same logic may apply to other approved expenses such as parking, lodging, childcare, meals outside the home, or additional medical costs, depending on the study's reimbursement policy.
Compensation Should Usually Follow Participation Already Completed
Compensation recognizes contributions such as time, effort, inconvenience, and research-related burdens. Once a participant has made those contributions, withholding the associated compensation simply because the person later withdraws can be difficult to justify.
FDA therefore states that payment credit should accrue as participation progresses. OHRP recommends payment schedules such as monthly or bimonthly payments in a six-month study, or payment after every two sessions in a twelve-session study.
The precise mechanism is the subject of prorating participant payment, but the underlying principle is that completed contribution and accrued compensation should remain connected.
Payment Does Not Necessarily Have to Be Handed Over Immediately Upon Withdrawal
Accruing payment and physically disbursing it are not identical.
FDA states that, when it does not create undue inconvenience or a coercive practice, payment to someone who withdraws may occur on the date when the participant would otherwise have completed the study or the relevant study phase. For a study lasting only a few days, for example, an IRB might permit everyone to be paid on one scheduled date even if someone withdrew earlier.
SACHRP similarly recommends periodic payment where feasible but recognizes that administrative constraints may sometimes justify holding accrued prorated amounts until the study ends.
Accrual
The participant has earned or become entitled to an amount through completed participation or incurred expenses.
Disbursement
The study actually transfers the accrued money to the participant.
A later payment date does not necessarily mean the participant has forfeited the amount.
A Genuine Completion Bonus Can Work Differently
Not every promised dollar must necessarily accrue visit by visit.
FDA permits a small proportion of the overall payment to be offered as an incentive for completing a study, provided the incentive is reasonable and not so large that it unduly induces participants to remain when they otherwise would withdraw.
SACHRP goes further in explaining why a completion incentive differs from reimbursement and compensation. An incentive may deliberately be tied to crossing a particular study "finish line" because its purpose is retention rather than repayment for expenses or recognition of contributions as they occur.
| Payment type |
If the participant withdraws |
Why |
| Reimbursement already accrued |
Generally retained or payable |
The participant already incurred the qualifying expense |
| Compensation already accrued |
Generally retained or payable |
The participant already contributed the associated time, effort, or burden |
| Payment for future activities |
Generally does not accrue |
The participant did not complete those activities |
| Genuine completion incentive |
May depend on reaching the defined completion point |
Its prospective purpose is specifically to encourage completion |
Calling Everything a Completion Bonus Does Not Solve the Problem
A study should not relabel most or all participant compensation as a "completion bonus" merely to discourage withdrawal.
SACHRP recommends that completion bonuses be used in studies that separately provide needed reimbursement and compensation. Otherwise, money described as an incentive may actually be functioning for participants as reimbursement or compensation, making its forfeiture ethically more problematic.
The purpose of each payment therefore needs to be established before deciding what happens after withdrawal.
Investigator-Initiated Withdrawal Needs Special Attention
Sometimes the participant does not choose to leave. The investigator may remove someone because of safety concerns, new exclusion criteria, study termination, or another protocol-defined reason.
SACHRP makes an important recommendation concerning completion incentives: if an IRB requires study termination because risks become excessive, or a participant must be removed because continuing participation would expose that individual to excessive risk, the participant should be treated as having completed participation for purposes of the promised completion bonus. The person fulfilled their responsibility rather than choosing to drop out prematurely.
This prevents a perverse incentive in which participants might hide adverse events because reporting them could cause removal and loss of a substantial bonus.
Withdrawal for Noncompliance Should Be Defined Prospectively
More difficult cases arise when investigators remove someone for noncompliance or failure to follow study procedures.
OHRP recommends that consent materials provide a detailed account of payment terms, including conditions under which participants receive partial or no payment and what happens if they withdraw or investigators remove them for medical or noncompliance reasons. SACHRP repeats this principle in its payment recommendations.
That does not establish that every form of noncompliance automatically justifies forfeiting payment. It means the issue should be addressed prospectively rather than improvised after a disagreement with a participant.
Withdrawal Should Not Retroactively Erase Legitimate Participation
Researchers sometimes focus on whether the participant delivered a complete dataset. Payment ethics asks a different question.
A participant may have spent hours completing legitimate study activities before withdrawing. The resulting dataset might be incomplete, but the participant's time was real. If the payment was compensation for that contribution rather than a purchase price for a complete dataset, incompleteness alone does not erase the basis for accrued payment.
Watch Out
Do not make ordinary reimbursement or compensation entirely contingent on producing a complete dataset. That can transform payment for costs and contributions into pressure to remain enrolled.
04 · A Practical Example
A Participant Withdraws After Four of Six Visits
Hypothetical Example
A Six-Visit Study With a Completion Bonus
A study has six visits. Participants receive approved transportation reimbursement for each visit, $40 compensation for each completed visit, and a separately disclosed $30 completion incentive after finishing all six visits.
Visits 1–4
The participant completes four visits, incurs approved transportation expenses, and accrues four visit-based compensation payments.
Withdrawal
Before Visit 5, the participant voluntarily decides not to continue.
Reimbursement
Approved expenses associated with the four completed visits remain payable because those costs were already incurred.
Compensation
The participant retains or receives the compensation accrued for the four completed visits.
Future visits
No compensation accrues for Visits 5 and 6 because those activities never occur.
Completion incentive
Whether the separate $30 bonus is payable depends on the prospectively approved terms governing that genuine completion incentive and the circumstances under which participation ended.
The crucial point is that withdrawal does not convert the participant's first four visits into unpaid participation. Each component is handled according to its actual purpose.
07 · A Quick Checklist
Before Finalizing Payment Rules for Participant Withdrawal
Check:
Separate reimbursement, compensation, and any genuine completion incentive.
Specify when reimbursement and compensation accrue during participation.
Avoid making all accrued compensation contingent on completion of a multi-stage study.
Define what happens when a participant voluntarily withdraws.
Define what happens when the investigator removes a participant for safety, medical, eligibility, or noncompliance reasons.
Ensure any completion bonus is separately identified and not so large that it unduly discourages withdrawal.
Distinguish when payment accrues from when it will actually be disbursed.
Describe the withdrawal-payment rules clearly in consent materials and obtain required ethics approval.
