Field help (LOTSIH4) 

For invoices, specify the lot to be issued.
Specifying it is not necessary in the following cases:

If the product is managed with serial numbers, only this number is necessary to determine the stock to issue.

If not, the lot, sub-lot and location (conditioned by the product management method) are needed.

For credit memos, if the product is not managed by lot, this field cannot be accessed. If the product is managed in mandatory or optional lot, the field availability depends on:

At the end of the entry, if no lot number has been entered, several cases can arise: