Answer
Without that map, teams compare demos against assumptions instead of against reality. ERP decisions get better when the process truth is visible first.
The most reliable documentation comes from walking through each process with the people who actually do the work, not just the managers who think they know how it runs. Frontline staff are usually the ones who can point to the shadow spreadsheet that patches a gap in the ERP, the manual reconciliation step nobody put in writing, or the exception case that happens every month but never made it into any process diagram. Skipping this step is the most common reason ERP evaluations end up comparing vendor demos against an idealized process that does not match daily reality.
Buyers should pay particular attention to exception handling, not just the happy path, since most operational pain comes from what happens when an order is short-shipped, a price override is needed, or a return does not match the original invoice. A vendor demo that only shows the clean version of order-to-cash proves very little if the current system's real value lies in how it handles the messy ten percent. Documenting that ten percent honestly, including the workarounds nobody is proud of, gives the evaluation team something real to test new candidates against.