Advances in Travel Management

Dear Experts,

I have come across a scenario in which client wants to edit the advances once entered by employee (end user in portal) after arriving at a certain advance amount for certain cases.

However as per the requirement I noticed that the advances once entered in an expense report cannot be edited. i.e. expense report number once generated the advance row is getting non-editable.

Is there any configuration setting which I had missed or this is standard behavior of SAP.

Please suggest.

Thanks,

Prakhar