IPMP (Inner Packs per Master Pack)

Amazon & D2C glossary · Harpy Media

IPMP (Inner Packs Per Master Pack) declares how many inner packs (case packs) a single master carton contains — the next layer up the packaging hierarchy from IPIP. Together the two attributes describe the full structure: master carton → inner packs → sellable units.

What is IPMP?

IPMP (Inner Packs Per Master Pack) declares how many inner packs (case packs) a single master carton contains — the next layer up the packaging hierarchy from IPIP. Together the two attributes describe the full structure: master carton → inner packs → sellable units.

Receiving operations read this hierarchy to know what they’re handling before they touch it: whether a carton opens into cases as expected, whether scans should count layers or units, whether the PO will receive cleanly in one pass. Get the hierarchy right and your shipment is a known quantity; get it wrong and the FC inherits a puzzle — priced in delays, discrepancy claims, and inventory accuracy that haunts the listing for weeks.

The cost of a wrong hierarchy

Misdeclared IPMP produces a specific accident pattern: scanners expecting the wrong layer count either over-count (counting packs as multiple cartons) or under-count (treating several packs as the shipment total), both of which write false numbers into your inventory — shortages where stock exists, phantom stock where it doesn’t. Add the slower path: shipments flagged for manual investigation wait days before selling, and each correction consumes a claim cycle. The root causes are mundane and always upstream: a factory that changed case configuration; a carton spec revised for freight efficiency without a data update; the classic setup error where the form was filled once from a draft that never matched production. None of these are exotic failures — they’re data drift, and data drift at scale is expensive.

Keeping the hierarchy honest

The full configuration sheet per SKU — units per inner pack (IPIP), inner packs per master (IPMP), carton dimensions and weights, and layer/pallet pattern — treated as a living document rather than launch-time paperwork. The update triggers: any packaging change (full stop — if it ships differently, its data changes first), a new supplier or production line (verify their configuration against your record before the first PO), and quarterly audit spot-checks (open one carton; the five-minute count catches drift early). Tie this discipline to your inbound programme choices: carriers and FC flows that trust declared data punish stale data most — and the flows that would catch the error slow you down instead. Accurate hierarchy data is what makes fast-flow inbound possible at all.

In practice

A vendor’s inbound starts failing periodic check-ins after a “minor” carton change improves container cube. Minor in cubic centimetres; significant in data: the new cartons held four inner packs where the record still declared six. Two POs run through receiving with mismatched counts before the pattern surfaces; the correction adds a week of investigation on top of the freight savings. The standing fix pairs them forever after: cube changes and attribute updates ship as one joint project.

How Harpy Media helps

Hierarchy-data discipline runs inside our inbound setup — we treat packaging changes as data events, because FC receiving only knows what the catalogue tells it.

IPMP FAQ

What is IPMP?

Inner Packs Per Master Pack — the number of case packs inside one master carton; with IPIP it fully describes your packaging hierarchy.

What happens if IPMP is wrong?

Scanners miscount, inventory records drift from reality, shipments stall in investigation, and discrepancy claims follow — all from a data field nobody rechecked.

When should hierarchy data be updated?

Whenever packaging changes, from a new supplier or line, or on any carton revision — update attributes and ship the change as one operation, then spot-check quarterly.