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MRP Planning Terms Glossary (Searchable Reference Table)

MRP conversations go wrong when two people use the same word for different things. This table gives the standard meaning of each term and shows where the planner meets it in an ERP planning run.

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Term	Short form	Meaning	Where a planner sees it
Gross requirements	GR	Total demand for an item in a time bucket before any supply is considered	Top row of the MRP record; from forecasts, customer orders and parent planned orders
Scheduled receipts	SR	Supply already committed, such as open purchase orders and released production orders	Second row of the MRP record, dated to expected receipt
Projected available balance	PAB	Expected on-hand stock at the end of a bucket after demand and supply	Row that triggers a new order when it falls below zero or safety stock
Net requirements	NR	The shortage left after on-hand stock and scheduled receipts are applied to gross requirements	Drives the size and date of a planned order
Planned order receipts	POR	Quantity MRP proposes to be received to cover net requirements	Shown by lot size rule; becomes a planned order in the system
Planned order releases	PORel	The same planned orders shifted earlier by the lead time	The date a buyer or shop must start the order
Lead time offset	LT	Time subtracted from the need date to get the order release date	Item master lead time fields, routing times, vendor lead time
Safety stock	SS	Buffer quantity planned to remain on hand to absorb demand or supply variation	MRP treats stock below this level as a shortage
Safety lead time	SLT	Extra days added so supply arrives before the need date	Alternative to safety stock when timing is the risk
Lot sizing rule	LS	Rule that converts net requirements into order quantities	Item planning parameters such as lot for lot, fixed or periodic quantity
Low level code	LLC	Lowest BOM level at which an item appears; MRP plans an item only after all its parents	Calculated at BOM change or net change run start
Bill of material	BOM	Structured list of components and quantities needed to make one parent	Explosion step that converts parent orders into child gross requirements
Explosion		Converting planned parent orders into dependent component demand through the BOM	Core MRP processing step each run
Netting		Offsetting gross requirements against available stock and scheduled receipts	Core MRP processing step each run
Pegging		Trace from a supply or requirement back to the demand that created it	Pegging or where-used-by-demand screens and reports
Net change planning	NC	Run that replans only items with changes since the last run	Daily or intra-day planning runs
Regenerative planning		Run that recalculates all planned items from scratch	Weekly or after major data changes
Planning horizon		How far into the future MRP plans	Run parameter; must cover cumulative lead time of the longest item
Time bucket		Unit of time used to group demand and supply, such as day or week	Planning calendar and MRP record column width
Demand time fence	DTF	Near-term window inside which forecast is ignored and only firm orders count	Item master planning time fence fields
Planning time fence	PTF	Window inside which MRP does not automatically change or create orders	Item master planning time fence fields
Firm planned order	FPO	Planned order protected from automatic MRP changes	Planner action to freeze a proposal
Action message		System suggestion to release, expedite, defer, cancel or change quantity of an order	Exception list the planner works through each day
Dependent demand		Demand for an item calculated from demand for its parent	Component requirements created by explosion
Independent demand		Demand from outside the plan such as customer orders, forecasts and service parts	Entered at end item level
Master production schedule	MPS	Plan of what end items will be built and when, which feeds MRP	Planned at end item or key item level
Available to promise	ATP	Uncommitted supply that sales can promise to new orders	Order promising and availability checks
Yield or scrap factor		Allowance that increases the gross quantity to cover expected losses	BOM component scrap and item yield fields
Phantom item		Subassembly that is exploded through rather than stocked or ordered	Item type or BOM flag in most ERPs
Order multiple		Increment to which order quantities are rounded up	Purchasing or lot size rounding fields

Term names vary slightly between APICS style material and individual ERP products. Field names in your own system may differ, so check your vendor documentation.

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How to use the glossary

Type part of a term in the search box, or scan the Where a planner sees it column to learn which screen or field the term maps to. The table exports to Excel or PDF, so you can attach it to a new planner's onboarding pack or an ERP implementation workbook. Terms are ordered roughly in the sequence an MRP run processes them: demand, supply, balance, orders, then controls.

The MRP record in one paragraph

Every MRP record is the same grid: gross requirements, scheduled receipts, projected available balance, planned order receipts and planned order releases per time bucket. The balance starts at on-hand stock. Each bucket adds receipts and subtracts demand. If the balance would drop below zero or below safety stock, MRP creates a planned order receipt in that bucket sized by the lot rule, then offsets it earlier by the lead time to get the release.

Terms people confuse

Several pairs cause repeated mistakes in planning reviews.

Gross vs net requirements: net is after stock and receipts, gross is before.
Scheduled receipt vs planned order: a receipt is committed, a planned order is only a proposal.
Demand time fence vs planning time fence: one controls which demand counts, the other controls whether MRP may change orders.
Safety stock vs safety lead time: quantity buffer versus timing buffer.
Net change vs regenerative: partial replan versus full replan.

Frequently Asked Questions

Is gross requirement the same as demand?

Gross requirement is the total demand placed on an item in a time bucket, including dependent demand created by parent orders and independent demand from customers or forecasts. It is demand before any stock or receipts are used to cover it.

What is the difference between a planned order and a scheduled receipt?

A planned order is a proposal created and changed freely by MRP. A scheduled receipt is a committed order such as a released shop order or a confirmed purchase order. MRP counts both as supply but only changes planned orders automatically.

Why does low level code matter?

MRP must know all demand for an item before it nets that item. The low level code sequences the run so a component is planned only after every parent that uses it, even if the component appears at several BOM levels.

Do all ERPs use the same MRP terms?

The concepts are common but the field names differ. For example some systems call the planning time fence a frozen period, and some split lot sizing into several procedure codes. Use this table for meaning and your vendor guide for field names.

If your planners still translate these terms between spreadsheets and the ERP, we can show how an AI assistant answers planning questions directly from your live MRP data.

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