What Are Positive and Negative Days?

Positive Days

• Defines a time window after a requirement date during which existing supply (inventory, purchase, production orders) can be used to fulfill demand without rescheduling.

• If a supply falls within positive days, MRP does not suggest rescheduling.

Example:

• Demand Date = June 10

• Positive Days = 3

• Supply on-hand = June 12 → MRP will use this supply without suggesting a reschedule, since it's within the +3-day window.

Negative Days

• Defines a time window before a demand date during which demand can be covered by earlier supply.

• If supply is available within negative days before the demand, it’s considered valid, and no new supply will be planned.

Example:

• Demand Date = June 10

• Negative Days = 2

• Supply available = June 8 → MRP will use this supply.

Where to Set Positive and Negative Days

1. Coverage Group Level

• Go to Master planning > Setup > Coverage > Coverage groups

• Set Positive days and Negative days

2. Item Coverage Level

• Go to Released products > Plan > Item coverage

• Override values per item and coverage group if needed

3. Static vs Dynamic Plan

• These parameters affect both static and dynamic master plans but mostly apply to requirement matching logic.

Note:

Use Net Requirements > Actions > Futures to see how supply and demand match up — this will visually show you how Positive/Negative Days are impacting MRP decisions.