Japanese to English Bus/Financial Accounting

This is in the context of training for the recording
(or handling) of revenues.
Here's the whole line:
旧〇〇は現状で「逆起票」という作業が発生しないため、操作はできたが処理内容を業務でどのように使うのか理解できないまま
教育を受けたという印象であった。
As you tell from the sentence, this clearly is an admittedly
obscure term. What might it mean?

Issuing a customer a 'post transaction credit'?
'Completing forms' after the fact?
Or does 逆 mean something else here?
Help!