Reading the UN code on your IBC
The block of characters on the cage plate is the container's passport. Four characters tell you what it is; the rest tell you what it is allowed to carry and until when.
- Sheet
- 27
- Revision
- 2026-10
- Scale
- 1:1
- Drawn at
- Peoria IL
31HA1/Y/0126/USA/M5678 — six fields, and every one of them can disqualify a container for a job.
Field by field
| Field | Example | Means |
|---|---|---|
| First digits | 31 | 31 = composite IBC for liquids; 11 = for solids, gravity discharge |
| Letter(s) | HA | H = plastic inner; A = steel outer. HZ = composite with other outer material |
| Last digit | 1 | 1 = liquids under pressure capability class; 2 = solids |
| Packing group | Y | X = PG I/II/III, Y = PG II/III, Z = PG III only |
| Date | 0126 | Month and year of manufacture — January 2026 |
| Country | USA | Country authorising the design type |
| Maker code | M5678 | Manufacturer and design type identifier |
What the code does not tell you
- Whether the tote is food grade. The UN marking is about transport safety, not food contact.
- What was last inside it. That is the declaration, and it is a separate document.
- Whether it has been re-tested. In the US, IBCs need periodic leak-tightness and full re-tests; the dates live on a separate plate or record.
- Whether the bottle has been replaced. A rebottled tote keeps its cage marking only if the rebuild is documented properly.
Try it on your own tote
Our decoder tool takes the code off your cage plate and explains each field, including what it rules in and out.
Legibility is a legal requirement, not housekeeping
A UN marking that cannot be read is a UN marking that does not exist. Painting over it, grinding it off or letting it corrode away removes the container from regulated service permanently — there is no re-certification path for an anonymous tote. Photograph the plate when a container arrives, keep the image with the serial, and never let anybody pressure-wash a cage plate at close range.
- Photograph markings at intake and store the image with the tote record.
- Never paint, wrap over or abrade the cage plate.
- Keep re-test records with the serial, not in a binder nobody can find.
- If the marking is gone, downgrade the tote honestly and sell it as non-regulated.
The characters people misread, and what it costs
| Confusion | Right | Wrong | Consequence of the error |
|---|---|---|---|
| Zero against letter O | 0126 | O126 | Date field fails to parse |
| One against letter I | 31HA1 | 31HAI | Category digit lost |
| Five against S | M5678 | MS678 | Maker code unverifiable |
| Y against V | /Y/ | /V/ | Packing group invalid |
| Missing separators | 31HA1/Y/0126 | 31HA1Y0126 | Fields cannot be split |
| Month and year swapped | 0126 = Jan 2026 | 2601 | Re-test window miscalculated by years |
- Photograph the plate rather than transcribing it. A photograph cannot misread itself and it is the evidence an auditor will want anyway.
- Shoot straight on, in daylight, filling the frame. An angled photograph is the commonest reason we cannot read a customer's image.
- If the plate is partly damaged, photograph it anyway — a partial code usually still gives the design type and the packing group.
- Store the image against your own asset number at intake. Four seconds, and it has settled every marking dispute we have had since 2024.
Check your transcription against the decoder
Paste the code in and it will tell you which field failed to parse rather than simply rejecting the whole thing.
Frequently Asked Questions
What does 31HA1 mean on an IBC?
The 31 means a composite IBC for liquids, H means a plastic inner receptacle, A means a steel outer, and the final 1 is the liquids class digit. The full code also carries packing group, date, country and maker code.
Does a UN marking mean the tote is food grade?
No. The UN marking is about transport safety, not food contact. It also does not say what was last inside the tote or whether the bottle has been replaced. Those come from the contents declaration and other records.
How do I read the date on the code?
The date field is month and year of manufacture. For example, 0126 means January 2026. Do not swap the order, since the guide notes that doing so can miscalculate the re-test window by years.
What happens if the UN marking is unreadable?
An illegible marking is treated as if it does not exist. The guide says there is no re-certification path for an anonymous tote, so it must be downgraded and sold as non-regulated. Never paint, wrap or abrade the plate.
Should I photograph the plate or type the code in?
Photograph it. The guide says a photograph cannot misread itself, and it is the evidence an auditor will want. Shoot straight on in daylight. Common typing errors include zero for letter O and one for letter I.
Next in the loop
Published 2025-12-02. 8 min read. Written by the crew that does the work, not a content agency.