Hello Jeffrey! Yes, you can adjust posted gifts appeals using IOM.
Gift Adjustment fields map directly to their specified field without any manipulation or changes from the source file. Gift adjustments import directly to the target gift and can not be added to a gift batch.
Gift adjustment fields:
* Amount * Appeal * Campaign * Date * Fund * Gift ID * Gift Import ID * Gift Subtype * Notes * Package * Post Date * Post Status * Reason * Use adj. GL post date