Payment refunds and reversals do adjust affiliate commission earnings, as long as you have not already generated the
masspay.txt file to pay out commissions for the month when the original sale occurred.
When you go to Seller Admin > Pay Your Affiliates to obtain your monthly commission report, that generates a fresh
masspay.txt file based on the current state of your Transaction Log at that moment for sales in the last completed calendar month. If anything affects that month's sales after you generate the masspay file, those changes will not be carried over into the next month's commission calculations. For instance, payments from the completed month may get refunded or reversed, or if you had a payment funded by eCheck late in the month, it could take several days into the next month for that check to clear. However, if you have not yet submitted the masspay file to PayPal, you can still regenerate a new masspay file before the end of the month, which would recalculate commissions to account for any late-breaking changes.
For this reason, we recommend generating your masspay file in the last half of each month, which should allow plenty of time for eChecks to clear or any refunds or reversals to be processed. You can also hold onto your masspay file for a while after generating it and before uploading it to PayPal, so you'd still have a chance to edit the commission totals in that month's file manually after the following month is already over. At present, we have no way to generate a masspay file for months prior to the last completed calendar month; this page explains how to review affiliate commissions prior to the last completed month.