How to Resolve an Underpaying Study with Bonus Payments

At Prolific, we believe in ethical rewards for participants.

From time to time, a study may fall below the minimum reward per hour (£5/$6.50 USD). This underpayment issue can arise when the study completion time has been underestimated - you can read more about what happens in this case here

If a study is noted to be underpaying, you may notice this yourself and/or receive a message from Prolific.

You should award bonus payments to any approved submissions, to increase the overall reward rate to meet minimum reward per hour requirements.

Please note that our regular pricing structure also applies to bonus payments, we charge a ~33.33% service charge on each bonus payment + VAT where applicable. 

More information about the estimated and average reward per hour can be found here.

How do I calculate the bonus reward due?

  1. Export your study data from Prolific (find out how to do this here).
  2. Prolific uses the median to work out your study's average completion time, so that extreme completion times do not skew the data.
    • You can calculate this in your export by using the MEDIAN function in your spreadsheet software. Follow these links for instructions on how to do this in:
    • Note that the data in your export is shown in seconds, so you'll just need to convert it into minutes once you've calculated the median
  3. Calculating bonus reward:
    • The overall reward per participant required for your study can be calculated as follows
      • Average time/60 x £5 (or $6.50) = minimum reward required
    • The bonus will be the difference between the initial and corrected reward.
      • e.g. (Bonus reward: corrected(2.30) - initial(2.00) = 0.30 

How do I reward a bonus to underpaid participants?

You can easily pay a bonus reward to all submissions in your study by selecting the "Bonus payment" button from your submissions page. 

Alternatively, to pay a variable bonus reward to multiple participants in your study, please refer to these instructions:

  1. Pause your study if it is still active.
  2. Export your study data from Prolific (find out how to do this here) and identify the participants you wish to reward. 
  3. Create a list with these participant ID's and the amount you wish to pay. 
  4. While viewing submissions for your study, select the "More" drop-down menu and go to "CSV bonus payments".
  5. Insert your list of participant ID's and the amount you wish to pay, separated by a comma. Screen_Shot_2018-12-07_at_14.45.58.png
  6. Click 'Pay Bonuses' 
    • Please note, this may take a moment to update. Do not attempt to pay the bonus payment a second time unless you receive a message to say the payments have failed. 
  7. If your study was paused, you will have to close your study early by selecting 'Stop' from the Action drop-down menu.
    • To obtain the remaining participants you require will need to 'Duplicate' your study, and publish a new version with the updated minimum reward per hour. 
    • To avoid participants retaking your study you will need to apply the 'previous studies' pre-screener. You can read more about this here.

For general information about bonus payments, see here.

We understand it can be difficult to determine an estimated completion time, we advise researchers to run a small pilot study on Prolific before launching to your full sample, and test it out on your colleagues/friends too. 

If you require further assistance please reach out to Prolific Support ( and we will be happy to help. 

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