The Purge Payments Start On Parameter is used to select if/how the Purge Payments function should be run each time a Closeout is saved.
Never - Do not run Purge Payments (it can still be run manually from the Closeout Menu).
Prompt - Prompts to ask if Purge Payments should run immediately after saving the Closeout.
Automatically - Runs Purge Payments automatically whenever a Closeout is saved.
Default = Prompt.
See:
Closeout - Contents