Low-Level-Code

Before you use Planning Worksheet to make any planning, make sure you have either:
1) Run the Calculate Low-Level-Code batch job (Manufacturing --> Product Design --> Calculate Low-Level-Code)
OR
2) Place a check mark at the Dynamic Low Level Code in the Manufacturing Setup.

If you did not do either one of the above mentioned steps, your planning worksheet will be not accurate.

What is the difference between Requisition Worksheet and Planning Worksheet

Requisition Worksheet is used to plan for items that are replenished by purchase and transfer while the Planning Worksheet is used to plan for items that are replenished by purchase, transfer and manufactured.