Yesterday we tried multiple times to put in an invoice and were met with an error message every time, eventually it seemed to go through but when we received the invoice it had combined all of the previous attempts into a much steeper invoice than we’re able to pay. Is there a way we can clear this invoice and just purchase credits instead? Thanks in advance!
Dear Darren
Welcome to the forum 
When it comes to system errors I am afraid that there is not a lot that we on the forum can do. Support is perhaps the only way forward. However, deleting cookies, or using a different browser (which will have different or no cookies) might help.
I am a bit confused by the word “invoice.” On the one hand it means request for payment, and on the other hand it means the same was “receipt” i.e. a detail of a payment that has already been made.
There are three or four types of such things that can be obtained from the GUI
From your account you can get a receipt-invoice showing all your payments to prolific.
From the Study action menu one can get detailed and non detailed invoices showing how much you have paid.
However to get a pre-payment invoice the only thing I can think of is the estimated cost shown on the study set up page when you have entered the approximate time and number of participants.
Other than that I can only think of asking support.
I am sorry I can’t be of more help!
Tim