UN markings
explained.
Photograph your data plate and attach it to the confirmation email. We will transcribe and explain it.
A marking like 31HA1/Y/0326/USA/M5261 reads: composite IBC, liquids, plastic inner with a metal outer frame, approved for packing groups II and III, manufactured March 2026, United States approval, maker code M5261. It certifies the assembly, not the bottle — which is why rebottling voids it and why a reconditioned unit is not automatically a compliant transport packaging.
Character by character
| Element | Meaning |
|---|---|
| 31 | Composite IBC intended for liquids. 11 = rigid for solids, 21 = rigid for solids discharged by pressure, 31 = liquids. |
| H | Plastic material of the inner receptacle. A = steel, B = aluminium, H = plastic, L = textile, M = paper, N = other metal. |
| A | Material of the outer casing. A = steel frame. So HA = plastic inner, steel outer — the standard caged IBC. |
| 1 | Design type: 1 = rigid outer casing providing full structural support. 2 = flexible outer. |
| /Y | Packing group. X = PG I, II, III. Y = PG II and III. Z = PG III only. Composite IBCs are almost always Y. |
| /0326 | Month and year of manufacture: 03 = March, 26 = 2026. |
| /USA | State authorising the design-type approval. |
| /M5261 | Manufacturer or approval-holder code assigned by that state. |
The other numbers on the plate
Below the marking string, a composite IBC plate normally carries a block of values that matter at least as much:
- Maximum permissible gross mass — the total filled weight the assembly is rated for. Typically 1,250 kg for a 1,000 litre unit.
- Tare mass — the empty weight as built.
- Test pressure — the hydraulic test value in kPa. Commonly 100 kPa for liquids.
- Maximum filling / discharge pressure, where applicable.
- Capacity in litres at 20 °C — the real number. This is where you learn your “275 gallon” tote is 1,000 litres.
- Stacking test load — the load the unit was tested to carry on top.
- Maximum permitted stacking load — what you may actually stack.
- Date of last leakproofness and periodic inspection — the field that decides whether the unit is currently compliant.
Why the test dates matter more than the marking
Under 49 CFR 180.350 in the US, composite IBCs used for hazardous materials require a leakproofness test and external inspection at 2.5 year intervals and a full periodic inspection at 5 years. The design-type marking is permanent; compliance is not. A 2016 unit with a beautiful 31HA1/Y marking and no test since 2019 is not a compliant packaging for regulated transport, whatever the plate says.
This is the single most misunderstood thing in the used IBC market, and it is why we do not advertise reconditioned units as UN-rated. If you need compliance, you need a current test record — see new units or ask us about re-testing.
What the plate tells a used buyer
Even when the rating is irrelevant to you, the plate is the most valuable thing on the container:
- Date code — a 2008 bottle in good condition is fine; it also tells you how much UV exposure to suspect.
- Capacity in litres — the actual volume, not the marketing name.
- Manufacturer code — predicts bottle format, thread type and wall thickness.
- Provenance anchor — the serial number this plate carries is what our prior-contents record is tied to. No plate, no provenance, no food-grade path.
That last point is why an illegible plate drops a unit to technical grade permanently, however clean it looks.
Common markings
| Marking | Type |
|---|---|
| 31HA1/Y | Composite, plastic inner, steel frame — the standard caged IBC |
| 31HA1/X | Same, approved for PG I as well — uncommon |
| 31H1/Y | Rigid plastic IBC, no outer frame |
| 31A/Y | Steel IBC for liquids |
| 11HA1 | Composite for solids, gravity discharge |
| 13H3/Y | Flexible IBC (bulk bag) for solids |
Where to find the plate
On the cage frame, usually on one of the upper horizontal members on a long side, or on a tab welded near a top corner. On some European units it is a paper label under a clear sleeve, which is exactly why so many are illegible.
Inspection checklistMarking questions
Does a used tote keep its UN rating?
The marking stays on the plate, but its usefulness expires. A UN rating certifies an assembly tested to a standard within a validity window — for composite IBCs, the periodic inspection and leakproofness test regime under 49 CFR 180.350 applies at 2.5 and 5 year intervals. An out-of-date unit is not a compliant packaging for regulated transport even though the marking is still physically there. For anything regulated, work from the test dates, not the marking.
What does the Y in 31HA1/Y mean?
Packing group. Y means the packaging is approved for packing groups II and III — medium and low danger. X covers I, II and III; Z covers III only. Composite IBCs are almost always Y, because packing group I liquids generally are not permitted in IBCs at all.
Why does a rebottled tote lose the rating?
Because the rating applies to the bottle and frame tested together as an assembly. Change the bottle and you have a different assembly that has not been drop-tested, hydraulically tested or stack-tested in that combination. It can be re-tested and re-plated, which is a service rather than a default.
I only store product on site. Do I need any of this?
No. UN markings govern the offering of hazardous materials for transport. If the container never leaves your facility with a regulated material in it, the marking is interesting history and nothing more — do not pay a premium for it.
Send us a photograph of the plate
We transcribe them all day. Attach it to the confirmation email and we will tell you what you have.