Catch‑Weight Traceability – Variable Weight Lots

This topic is part of the SG Systems Global regulatory & operations glossary.

Updated October 2025 • Traceability & Execution • WMS, MES, GS1, Food, Pharma

Catch‑weight products are items whose actual weight varies unit‑to‑unit (e.g., cuts of meat, blocks of cheese, bulk API drums, syringes filled by weight). They demand controls that pair identity (GTIN/lot/SSCC) with measured net weight at each handling point. Operationally this blends MES and WMS discipline: scan to identify, weigh to quantify, and write tamper‑evident records under Data Integrity/Part 11/Annex 11.

“If you can’t prove the actual net weight tied to the actual lot, you don’t have traceability—you have guesswork.”

1) What “Catch‑Weight” Really Means

Each unit is unique by weight. You cannot treat a 2.01 kg pack and a 2.48 kg pack as the same “2.25 kg average.” Correct practice is to weigh each handling unit (unit/inner/case/pallet) using gravimetric devices, apply tare, and record net weight with the identifier that will travel downstream (label or SSCC). For regulated industries this is part of end‑to‑end lot genealogy and batch genealogy.

2) Master Data & UoM—Design for Variability

• Flag SKUs as variable weight; maintain dual UoM (EA↔weight) and tolerances (per unit, per case).
• Define recipe consumption on actual mass (not nominal) with scaling basis and, where relevant, potency adjustment.
• Require label artwork variants for variable‑weight declarations where country law applies; verify at line via label verification.

3) Weigh Points—Where Weight Must Be Captured

• Inbound: Goods Receipt → weigh each unit or case; bind weight to lot and SSCC; enforce dock‑to‑stock controls and incoming inspection as required.
• Pack‑off: From production into retail/cases; integrated load‑cells with audit trails; respect TNE/legal‑for‑trade limits.
• Outbound: Pick/ship confirmation must reconcile order quantity to actual shipped weight with directed picking, FEFO, and case/pallet GS1‑128 scans; exchange via ASNs.

4) Identity & Barcodes—The Glue

At minimum encode GTIN (AI 01), Lot (AI 10), and counts/expiry where applicable. For weight you have two options:

• In‑barcode weight: Include AIs like AI 310x/320x for net weight; needs printer/scanner readiness and strict barcode validation.
• In‑system binding: Store the measured weight against a unique pack/case ID (often an SSCC) and share via EPCIS events.

Either way, no scan = no ship. Mixed‑lot cases are a risk magnet—avoid them or label to the stricter of the contained lots and document via MRB if unavoidable.

5) Genealogy—From Unit to Pallet to Customer

Genealogy must connect unit→inner→case→pallet using parent‑child relationships and retain weights at the lowest practical level. This enables credible recall readiness, supports GDP, and satisfies FSMA 204 KDE/CTE expectations. Use location topology, bin control, and directed put‑away to keep status and lots segregated.

6) Inventory, Costing & Planning—Numbers Must Add Up

• Consumption: Backflushing fixed weights into variable‑weight reality is a fantasy. Consume on backflush only when the system knows the actual weights; otherwise post on scan/weigh.
• Mass balance: Reconcile inputs↔outputs with mass balance, monitor yield variance and WIP.
• Allocation: Use dynamic lot allocation and FEFO; respect Quarantine/Hold so nothing ships before lot release.

7) QA, Compliance & Inspections—What Auditors Expect

Auditors will ask to demonstrate: (1) the device integration path from scale to record (no editable spreadsheets), (2) identity‑to‑weight binding with audit trails, (3) review‑by‑exception in eBMR/WMS, and (4) disposition controls from status to finished goods release. In pharma/device, catch‑weight is covered by general GMP/quality system principles (21 CFR 211/820), not by DSCSA unit serialization (DSCSA)—don’t confuse the two.

8) Failure Modes—Common Mistakes (Don’t Do These)

• Using nominal weights to book inventory or to pick orders. It corrupts valuation and ruins recall math.
• Printing labels with weight but not tying the scale data to the scanned ID in the system.
• Ignoring tare or letting operators key in weight manually.
• Mixing lots in a case without deliberate control and documentation—creates ambiguity in genealogy.
• Managing variable weight in spreadsheets. Part 11/Annex 11 and basic retention/archival expectations make this a liability.

9) How This Fits with V5 by SG Systems Global

V5 Solution Overview. The V5 platform binds identity and weight at the point of use. Scale drivers are validated; audit trails are immutable; and cross‑module events are EPCIS‑ready.

V5 MES. V5 MES captures pack‑off weights with enforced dual verification when required and writes directly to the eBMR for QA review‑by‑exception.

V5 WMS. V5 WMS enforces inbound catch weighing, directed picking, dynamic allocation, and scan‑verified handover at Dock Loading.

V5 QMS. V5 QMS governs procedures, approvals, deviations/CAPA, and supplier controls so weight errors trigger real corrective action—not wishful thinking.

Bottom line: With V5, catch‑weight stops being “special handling” and becomes how your plant runs. Real weights, real genealogy, defensible release.

10) Metrics That Prove Control

• Weight capture coverage: % of variable‑weight units shipped with a recorded net weight bound to ID.
• Label compliance: Barcode grade/validation pass rate; label/scan exceptions per 1,000 packs.
• TNE/over‑under events: TNE exceedances per lot and corrective action cycle time.
• Mass balance delta: % difference between input mass and shipped output (by lot).
• Recall drill speed: Time to identify affected units/cases/pallets; OTIF impact of quarantines.

11) FAQ

Q1. Do I have to encode the weight in the barcode?
No. You can encode weight (e.g., AI 310x/320x) or bind the measured weight to a unique pack/case ID and exchange via EPCIS. Choose one and do it consistently, with validation.

Q2. How is this different from DSCSA/UDI serialization?
DSCSA/UDI track identity of saleable units; catch‑weight controls the quantity. You still need GTIN/lot (and UDI if devices), but variable‑weight handling is governed by good GMP/GDP practice, not DSCSA itself (DSCSA, UDI).

Q3. Where must QA be involved?
Approving weighing SOPs, verifying scale qualification, enforcing audit trails and Part 11 e‑signatures, and holding lot release until anomalies are resolved.

Q4. Can we average weights to simplify?
Not for traceability or label claims. Averaging hides risk and fails recalls. Control by unit, then summarize by pallet/shipment for customers.

Q5. What about mixed‑lot cases?
Avoid them. If unavoidable, create a new handling unit ID (e.g., SSCC), document composition in genealogy, verify labels, and route through MRB with QA approval.

Q6. Which regulations hit hardest?
General GMP principles (21 CFR 211, 820), GDP, Part 11/Annex 11 for data integrity, and—if food—FSMA 204 KDE/CTE mapping. Auditors will test your scale→record chain and recall drill.

Related Reading
• Weighing & Labels: Catch Weighing | Tare | Load Cells | TNE | GS1‑128 Case Label | GS1 AIs | Barcode Validation
• Identity & Genealogy: GS1 GTIN | Lot (AI 10) | SSCC | EPCIS | End‑to‑End Traceability | Batch Genealogy
• Execution & Control: MES | WMS | Directed Picking | Dynamic Lot Allocation | FEFO | Pack & Ship
• QA & Data Integrity: eBMR | Data Integrity | Audit Trail | 21 CFR Part 11 | Annex 11 | Lot Release