Hi everyone. I tried to search for an answer about this problem but I think I am not lucky enough so I created this post.
I tried to display lead time for finished items and materials on MRP report. I input data into “New item lead time”. The lead time displayed well for materials. However, no matter what I input for “Manufacturing”, the lead time for finished items always showed 1, even I tried very large sale order in MPS.
Appreciate a little help from you guys. Thanks in advance!
This behavior is actually by design in ERPNext MRP, not a bug.
In ERPNext, the MRP report does NOT calculate finished goods lead time from the “Manufacturing Lead Time” field in Item Master.
That field is mainly used for delivery planning and promise dates, not for MRP planning.
MRP calculates lead time for finished items only from the BOM and Routing, not from the Item.
Here is how it really works:
For Raw MaterialsMRP uses:
Item → Lead Time (Days)
So you correctly see the lead time for materials.
For Finished GoodsMRP completely ignores:
Item → Manufacturing Lead Time
Instead, it uses:
BOM → Routing → Operation Time → Workstation Time
If no routing or operation time is defined, ERPNext assumes default 1 day, which is exactly what you are seeing.
That is why even if you enter 50, 100, or 500 days in Manufacturing Lead Time, MRP will still show 1 day.
This is a common confusion among ERPNext users.
Hope this helps 
— ERPens
Thank you for your detailed reply!
I tried to do delete everything about routing and start from zero, but no luck for me. If it doesn’t bother you too much, I would like to describe what I’m doing in more details. After I delete all things related to Manufacturing lead time and Capacity, I got 0 lead time in MRP report 
When I talked about “Item lead time”, I was referring about “Item lead time form”, which includes Manufacturing and Purchasing lead time in it, as shown in images below
When I input data into “Purchase time”, the “Lead time” change immediately in MRP report (as shown as 12 in the image)
However, as described before, when I input data into “Manufacturing time”, it will only show 1 for Lead time in MRP report. If I delete all data in “Manufacturing time”, it will show as 0 lead time.
I think I have done the routing completely, it even shows lead time as 13 in Demand tab in “Master Production Schedule”
P/s: I can only send 1 image as new user
When I talked about “Item lead time”, I was referring about “Item lead time form”, which includes Manufacturing and Purchasing lead time in it, as shown in images below
When I input data into “Purchase time”, the “Lead time” change immediately in MRP report (as shown as 12 in the image)
However, as described before, when I input data into “Manufacturing time”, it will only show 1 for Lead time in MRP report. If I delete all data in “Manufacturing time”, it will show as 0 lead time.
You need to define the lead time for FG as well
Thanks for your response. I will check again one more time
