What makes these two versions different is the purpose of its running within the business established process in manufacturing accounting. For example, if you are processing work orders before reaching the status of full completion or your work order, this action is commonly called ‘Work In Process’ or WIP, denoting that the order it is not yet fully completed on the shop floor but that journal entries are been generated progressively before reaching the completed status.
Then, when the work order reaches the final status reflecting that all inventory and routing activity has been fully completed, therefore, ready to run P31802 in final mode for the last time (right before generating variances) this step is known as P31802 Completions or manufacturing accounting completion.
This is a user defined process, as it is not mandatory to run one version or the other or both. The definition of the business process can accommodate both runs, or only one. One of the most important keys for WIP and Completions versions is the work order status defined by user and that will be data selected and/or updated for the work orders that are been processed. User can define if there will be or not a status for WIP and a different status for final completion in UDC 00/SS, or use the same for both. The other key is the Variance Flag (PPFG) that resides in the Work Order Header.
For more details on P31802 program setup and information on (PPFG), review Knowledge Document Creating Manufacturing (WIP) Journal Entries (Document ID 1579651.1) and Purpose of the Variance Flag (PPFG) In Manufacturing (Document ID 661187.1).