UN Markings: The Date That Matters Is Not the One People Read
Reading this because you are specifying, buying or selling containers? Send the details and a grader answers in writing, usually the same business day.
A UN design-type marking is permanent; compliance for regulated transport is not. Under 49 CFR 180.350 composite IBCs need a leakproofness test and external inspection at 2.5 year intervals and a full periodic inspection at 5 years. The marking tells you what it was; the test dates tell you what it is.
This is the most misunderstood thing in the used IBC market, and it is misunderstood in a direction that gets people into trouble rather than out of it.
Somebody sees 31HA1/Y stamped on a cage, concludes the tote is a UN-rated packaging, and loads a regulated liquid into it. The marking is genuine. The conclusion is wrong.
What the marking actually certifies
A marking like 31HA1/Y/0326/USA/M5261 records a design-type approval. Read left to right:
| Element | Meaning |
|---|---|
| 31 | Composite IBC for liquids |
| H | Plastic inner receptacle |
| A | Steel outer casing — so HA is the standard caged tote |
| 1 | Rigid outer casing giving full structural support |
| /Y | Approved for packing groups II and III |
| /0326 | Manufactured March 2026 |
| /USA | State that authorised the design-type approval |
| /M5261 | Manufacturer or approval-holder code |
That is a statement about a design that passed a drop test, a hydraulic test, a stack test and a leakproofness test — at a point in time, as an assembly, under the authority of a named state.
It is stamped or plated on, and it does not come off. Which is exactly why it is misleading: the marking outlives the compliance by many years.
The field that actually governs
Below the marking string, a composite IBC plate carries a block of values. Buried in it is the one that decides whether the unit is currently a lawful packaging: the date of the last leakproofness test and periodic inspection.
In the United States, under 49 CFR 180.350, a composite IBC used for hazardous materials requires:
- An external visual inspection and a leakproofness test at intervals not exceeding 2.5 years.
- A full periodic inspection — external, internal, and including the leakproofness test and a check of all service equipment — at intervals not exceeding 5 years.
- An additional inspection after repair, remanufacture or any event affecting integrity.
A 2016 unit with an immaculate 31HA1/Y marking and no recorded test since 2019 is not a compliant packaging for regulated transport. The marking says what it was built as. The test record says what it is.
Why we do not advertise reconditioned units as UN rated
Because almost none of them are, and saying otherwise would be the easiest and most dangerous lie available to us.
A reconditioned tote has typically spent years outside any test regime. We air-hold test every Grade A unit and above at 3 psi, which is our own quality control and is not the same thing as a 49 CFR periodic inspection performed by a registered party with a retest marking applied.
So the honest statement is: our totes carry whatever design-type marking they were born with, they are not currently certified packagings, and if you need a compliant packaging you need either a new unit or a specific retest.
Rebottling voids it entirely
This one is structural rather than administrative. A UN approval covers the bottle and the frame tested together, as an assembly. Replace the bottle and you have a combination that has never been drop-tested, hydraulically tested or stack-tested in that configuration.
So a rebottled unit — new virgin bladder, reclaimed cage — is not UN rated, and no amount of the old marking still being physically present changes that. We date-mark rebottled units with the rebottle date and our batch reference specifically so there is no ambiguity about what happened to them.
If you do not ship regulated liquids
Then none of this matters and you should not pay for it.
UN markings govern the offering of hazardous materials for transport. If the container never leaves your site with a regulated material in it — storage, irrigation, wash water, ballast, dust control, in-plant transfer — the marking is interesting history and nothing more.
We regularly talk buyers out of paying a premium for a UN-marked unit they have no transport application for. It is an easy upsell and a pointless one.
What the plate is worth to everybody else
Even when the rating is irrelevant, the plate is the single most valuable thing on the container:
- Prior contents — the basis of every grade above technical, and all food-grade eligibility.
- Capacity in litres at 20 °C — the real volume, not the marketing name. This is where you learn your '275 gallon' tote is 1,000 litres.
- Manufacturer code — predicts bottle format, wall thickness and, critically, whether the outlet is 2-inch buttress or S60x6.
- Date of manufacture — tells you how much UV exposure to suspect.
- Maximum permitted stacking load — what you may actually stack, as distinct from the test value.
- Tare mass — for your own gross weight and freight calculations.
Which is why an illegible plate drops a unit to technical grade permanently. It is not a formality. It is the loss of every fact about the object.
825 words · published 28 April 2026 by Dale Prichard, Senior grader at IBC Tote Market LLC. We correct posts rather than quietly deleting them; if something here is wrong, tell us and we will say what changed.