Compliance · September 21, 2021
Reading the UN Plate on Your Cage
31HA1/Y/0426/USA/M1234. Five fields, each of which tells you something you probably need.
The short version
31 is a composite IBC for liquids, H is a plastic inner receptacle, A is a steel outer casing, Y covers packing groups II and III. The marking doesn't expire — the container's authorisation does, every 2.5 and 5 years.
Most people who own IBCs have never read the plate riveted to the cage. It carries more information than they expect, and one field on it decides whether the container can legally move a regulated product tomorrow.
Finding it
Usually riveted or bonded to a long side of the cage, about two thirds of the way down, near a corner post. On some designs it's moulded into a raised panel on the bottle itself.
Three other places carry identification worth knowing about: a moulded date clock or date string on the bottle near the neck, a stamped code in the tubular frame near a weld on some manufacturers, and a moulded identifier on composite and plastic pallet bases.
Decoding it, field by field
| Field | Example | Meaning |
|---|---|---|
| Type digits | 31 | Rigid IBC for liquids (11 = solids by gravity, 21 = solids under pressure) |
| Inner receptacle | H | Plastic — the bottle |
| Outer casing | A | Steel — the cage (B aluminium, N other metal, H plastic, D plywood) |
| Category | 1 | Designed for liquids under the standard's pressure conditions |
| Packing group | Y | Approved for PG II and III (X covers I–III, Z covers III only) |
| Build date | 0426 | April 2026 — month and year of manufacture |
| Country | USA | State that issued the design type approval |
| Manufacturer code | M1234 | Identifies the manufacturer or approval holder |
| Max gross mass | 1250 kg | Container plus contents — about 2,756 lb |
| Capacity | 1040 L | Nominal — 1,040 L is 275 US gallons, 1,000 L is 264 |
| Test pressure | 100 kPa | Hydraulic test pressure applied at qualification |
| Last test date | 0929 | Most recent leakproofness or requalification test |
The retest intervals
| Interval | Requirement | Scope |
|---|---|---|
| Every 2.5 years | Leakproofness test and external inspection | Containment integrity, service equipment, marking legibility |
| Every 5 years | Full requalification | Leakproofness plus internal and external inspection and structural verification |
| After any repair | Retest before return to service | Any repair affecting containment or structural equipment |
| Before each use | Visual check by the offeror | Damage, leakage, marking legibility, retest currency |
That last row is the one that catches people. It's your obligation as the offeror, it's not marked on anything, and nobody sends a reminder.
What a plate does not prove
A UN marking proves the design type was tested and approved. On its own it proves nothing about whether this particular container is currently authorised.
Three things have to be true simultaneously: the marking is genuine and legible, the container is within its retest window with the test date marked, and any repair or reconditioning was done by a facility registered to do it.
This is where a great deal of used-container selling becomes dishonest. A rusty cage with a legible plate, from a yard that has never held a reconditioner registration, is not a compliant container. It's a container with a plate on it — and because you are the offeror, the consequence lands on you.
Three questions for any seller of UN-marked stock
- 1What's your reconditioner registration number? Only a registered facility may restore a marking after repair.
- 2What's the most recent test date marked on the container, and can I see the record?
- 3What repairs were performed, and were they retested afterwards?
When the plate and the bottle disagree
On a properly rebottled container, the cage plate shows the original build date and the bottle moulding shows a recent one. That isn't a discrepancy — it's the expected signature of the work, and it's one of the quickest ways to identify a rebottled unit.
What should concern you is the reverse: a recent plate on a visibly old, corroded cage. That suggests a plate has been transferred or applied without the corresponding work.
And if none of this applies to you
Storing water, fertilizer or non-regulated chemistry on your own property requires no UN marking at all. Paying a compliance premium for a container that will never leave your site is money better spent on a full-port valve. Compliance matters when the container moves on a public road with regulated product in it — and only then.
Published September 21, 2021 · Updated November 4, 2025 · Filed under Compliance
