When you use the ERM Import Payment window to import a payment from a csv file, the source csv file being imported is then locked and cannot be renamed, or saved over, until the user exists GP.

Once the user exits GP the file again becomes available for rename or saving over.

It would be nice to be able to rename the file while you are still in GP
Ideas Administrator

Thank you for your suggestion. We have reviewed this functionality ask previously.  Unfortunately, given the impact throughout the entire system and on customizations, this is not something we can consider at this time.. 
Best regards.