You may need to break it up into multiple refunds instead of trying to make ONE big refund. The concept is that there is a single payment that needs to be refunded. Sounds like you want to refund more than the amount of one payment. So, got into all the payments you want to refund and UNapply any applications to specific invoices. Check the box to apply the payment to a future invoice (this will result in an unapplied amount that can be refunded.) 

Then, try to refund one payment at a time. Maybe change the default description to be more like "Refund Part 1 of 4 for a total of $X." Then click on the unapplied payment that you want to refund. Repeat until you have refunded the total that you want to refund.

Hope that helps.

Nancy Duhon, Esq.
Duhon Technology Solutions, LLC
Master Certified Consultant for Sage Timeslips
Providing individual Consultations and Third Party Remote Desktop Support - including older/unsupported versions.
404-325-9779
[email protected]

This is a confusing aspect of Timeslips/accounting.  I don't know exactly how to fix it but part of the problem (I think) is that you are creating the refund from the A/R menu and there is no associated charge.  It depends how you entered the payment. Was it entered as an account receivable or is it in client funds (or something else)?