Lenae,
There is an urgent sales order of 10 units coming in soon. There is a need to do a build of 10 units in June (Assuming the current period is June). What do you do in the perspective of a planner?
Create supply orders such that the product arrives in the shipping warehouse prior to the expected delivery date. The nature of these supply orders (e.g. should they be planned orders/production orders/purchasing reqs/Purchase orders/etc etc etc) is dependent upon your company's business processes.
Eventually, the sales order is not accepted.
I assume that you mean that your company, for business reasons, elected not to enter the order into your SAP system. Please confirm.
Planner manually creates a plan order for 15 Nov of 5 units.
Well, you haven't said anything about why a planner would have done such a thing, nor what his methodology was. But, OK, lets accept this.
Rerun MRP.
Explains what happens.
Well, sorry, I am not going to explain what MRP does, it does a lot of things. If you want to know more about what MRP does, try SAP help.
Planning Process - SAP Library
Read this page, and all the topics on the left hand side to get a good basic understanding of 'what happens'.
If you are asking what happens to the manually created planned order during MRP, that depends upon whether or not the planner elected to enter the planned order as 'firmed'. It also depends upon the parameters that were entered when executing MRP.
I really think you need to speak to your local planners. They will tell you what your company's standard business processes are, and how these business processes are executed in SAP.
Best Regards,
DB49