When a packaging-related incident happens — a child suffocation, a recalled product line, a regulator-mandated audit — the first thing the lawyer or investigator asks is: can you trace this specific bag back to the lot it was made in?
Most poly packaging buyers can't answer that question. The bag has no number. The case has a generic SKU. The PO references a quantity, not a lot. The supplier may or may not have a record. The chain of custody dies somewhere between the converter and the warehouse — and that's where liability lives.
This is the part of supplier due diligence that gets skipped because it never matters. Until it does, and then it's the only thing that matters.
What lot traceability actually means
A lot trace is a documented chain from the bag in question back to its production lot, and from that lot back to the inputs that produced it. For a vertically integrated poly bag manufacturer, that chain has six links:
- The bag carries a roll number printed in the corner — small, ink-on-film, not a sticker that falls off.
- The roll number maps to a conversion run — date, machine, operator, quantity.
- The conversion run ties to the film master roll it ran from.
- The film master roll ties to an extrusion run — date, line, operator, inline gauge readings.
- The extrusion run ties to the resin lot it ran on — supplier, supplier lot, certificate of analysis.
- The resin lot ties to the bill of lading from the resin supplier.
Each link is a piece of paper or a database row that a regulator, insurance underwriter, or class-action lawyer can request and follow. The chain is the thing that makes the bag investigable.
Why most poly bags can't be traced this way
The economics of cheap poly packaging are built on substitution. A catalog distributor sources bags from whichever converter has the best price that month, who may have sourced film from whichever extruder had inventory that week, who may have run on whichever resin lot was cheapest at the cracker. By the time the bag arrives at your dock, the chain is three or four hands deep — and at least one of those hands kept no records.
When the regulator asks, the answer is “we bought this from Distributor X.” Distributor X says “we bought this from Converter Y.” Converter Y says “our records don't go back that far.” The bag is now an orphan.
The orphan bag is the lawyer's favorite kind of bag. It's also the regulator's signal that the entire supply chain is uninvestigable — which is the worst signal a supply chain can send.
What CPSC asks for in a suffocation incident
- The specific bag involved, or a representative sample from the same lot.
- The lot number or production date code.
- The manufacturer's full chain of custody — distributor, converter, extruder, resin supplier.
- The bag's compliance documentation — gauge, warning print, vent specifications.
- The brand owner's purchase records for the lot.
If the bag is traceable, this is a two-week paperwork exercise. If it's not, it's an open investigation that compounds the brand's reputational and legal exposure for months — and signals to CPSC that the brand's supplier chain is not under control.
What Amazon asks for in a marketplace incident
- Proof the bag met FBA polybag specifications at the time of shipment.
- Lot or batch documentation.
- The supplier's certifications and country-of-origin documentation.
- A corrective action plan if the lot is suspected of non-conformance.
A seller with traceable bags can get a suspended ASIN reinstated in days. A seller without can spend months reconstructing the supply chain — sometimes finding the original lot is unrecoverable, which means the ASIN stays suspended through peak.
What a class-action lawyer asks for in discovery
- All production records for the relevant SKU over 3–5 years.
- All supplier change records — including silent substitutions.
- All quality assurance records, including any documented non-conformance.
- All correspondence with the supplier on spec changes, complaints, or returns.
If the brand can produce these records — neatly, in a chain, with dates that match — the lawyer's strongest argument (that the supply chain was uncontrolled) collapses. If the brand can't, the discovery process becomes the case.
Five questions to ask your supplier before you need them
- Does every roll / case / bag carry a unique identifier we can trace back to a specific production lot?
- Do you retain production records for at least five years — operator logs, gauge readings, resin certs?
- Can you produce a full chain-of-custody document for a single bag, on request, within 48 hours?
- Are your resin suppliers documented to a specific supplier-lot level, or only to “LDPE/LLDPE generic”?
- If you've made a spec change for our SKU in the last 12 months, is it documented in writing with our sign-off?
The cost of traceability vs the cost of the missing record
A lot-traced poly bag costs more than an untraceable one — sometimes 5–15% more, depending on the program — because the documentation overhead is real. Inline gauge monitors, lot-coded printing dies, retained samples, database systems, audit-ready records all cost money the supplier has to recover.
A single suffocation incident with an untraceable bag, in the lowest-cost scenario where insurance covers the settlement, runs an estimated $250,000–$2M in defense costs and reputational damage. In the highest-cost scenario where insurance denies coverage because the brand couldn't document supplier diligence, the cost is the company.
The 5–15% premium for a lot-traced bag is the cheapest insurance line item your operations team will negotiate. The question isn't whether you can afford it. The question is whether you can afford to not have it the one week you need it.