How to decode the UN certification code stamped on an IBC tote so you know what it is rated to carry and how it was tested.
Stamped into the cage label or molded plate of most IBC totes is a string of letters and numbers that looks like gibberish until someone explains it: something like 31HA1/Y/0524/USA/... This is the UN certification mark, and it is one of the most important things to understand if your tote ever carries a regulated material. It is, in effect, the container's birth certificate and rating in one code.
Why the Marking Exists
IBCs that transport hazardous materials must be designed, tested, and certified to international standards developed under the United Nations and adopted in the United States by the Department of Transportation. The UN marking certifies that this design of container passed a battery of performance tests: drop, stacking, leakproofness, hydraulic pressure, and more. The mark is your evidence that the tote is authorized for a given class of contents.
Breaking Down the Code
The code is read piece by piece. Using a common example, here is what each section tells you:
- ✓UN symbol or the letters UN: identifies this as a United Nations certified package
- ✓31: the IBC type and design, where 31 indicates a composite IBC for liquids; a 11 would indicate solids
- ✓HA1: the material code, where H is rigid plastic and the combination indicates a plastic inner with an outer (steel) framework
- ✓Y: the packing group rating, covering medium and low danger goods (Packing Groups II and III)
- ✓0524: the month and year of manufacture, here May 2024
- ✓USA: the country that authorized the certification
- ✓A manufacturer or approval reference, plus a stacking load and maximum gross mass figure
Read together, that string tells you the tote is a composite plastic-in-steel IBC for liquids, rated for medium-danger goods, built in May 2024, certified in the USA.
Packing Groups: X, Y, and Z
The single letter in the middle is worth dwelling on because it sets the danger level the tote may carry:
- ✓X: rated for Packing Group I, II, and III, the highest danger materials
- ✓Y: rated for Packing Group II and III, medium and low danger
- ✓Z: rated for Packing Group III only, low danger
Most general-purpose IBCs carry a Y rating. If your material is a Packing Group I substance, you need an X-rated tote, full stop. Matching the packing group of your product to the packing group on the tote is non-negotiable for compliant transport.
Stacking Load and Gross Mass
Following the main code you will usually find additional figures: a stacking test load in kilograms and a maximum permitted gross mass. The stacking number tells you how much weight the tote was tested to bear on top of it; exceeding it risks crushing. The gross mass is the total allowed weight of the tote plus contents. Both are real operational limits, not just paperwork.
The 12-Month and 30-Month Rule
A certification is not permanent. Totes used for hazardous materials transport are subject to periodic inspection and retest requirements: a more thorough leakproofness and inspection at set intervals (commonly referenced as 12-month and 30-month checks under the regulations). A tote whose retest date has lapsed may not be legal for hazmat transport even if it looks fine. The dates and inspection records travel with the container.
Reconditioned and Remanufactured Totes
When a tote is rebuilt, the rules around its markings get specific. A simple reconditioning that restores the original design may retain the original UN mark, while a remanufactured IBC may need to be recertified and remarked. This is exactly why working with a knowledgeable reconditioner matters: the marking has to honestly reflect what the container is and what it has been tested to do.
When the Marking Matters Most
If you are only storing non-hazardous water, soap, or food product, the UN mark is informational. The moment a regulated hazardous material enters the picture, that stamped code becomes a legal requirement. Learn to read it, match it to your product's packing group, check the manufacture and retest dates, and you will avoid the most common and most expensive compliance mistakes in bulk shipping.
Put this to work
We buy, sell, recondition and haul totes across New England — reuse-first, every time.