Certificate Stamp (Cert) on Corrugated Boxes Explained

What Is the Certificate Stamp?

The certificate stamp, commonly called the “cert,” is a circular or rectangular printed mark found on the bottom flap of corrugated shipping boxes. It is functionally identical to the Box Manufacturer’s Certificate (BMC) and represents the manufacturer’s certification that the box meets defined strength and construction standards. Every corrugated box used for shipping should carry this stamp to comply with freight carrier classification rules.

The cert serves as a quick reference for anyone in the supply chain who needs to verify what a box is rated to handle. Warehouse workers, freight carriers, and quality inspectors all rely on this stamp to confirm that packaging is appropriate for its contents and intended shipping method.

How to Read the Certificate Stamp

The certificate stamp contains several lines of information packed into a compact format. At the top, you will typically find the board type, such as “single wall” or “double wall.” Below that is the strength rating, expressed as either an ECT value (e.g., “32 ECT”) or a Mullen burst value (e.g., “200#”). The stamp also lists the maximum gross weight the box can contain and the maximum combined outside dimensions (length + width + height).

The bottom of the stamp identifies the manufacturer. For boxes produced by President Container, you will see our name or identifying symbol along with our facility location. This traceability is important for quality tracking and accountability.

Why the Certificate Stamp Matters

The cert is more than a formality. Freight carriers can reject shipments in boxes that lack a proper certificate stamp or that contain goods exceeding the stated weight or size limits. If goods are damaged during transit and the box was improperly rated, claims may be denied. The stamp is your assurance that the box was manufactured to handle the loads specified.

For businesses managing multiple packaging SKUs, the cert stamp is a fast way to distinguish between box grades on the warehouse floor without referencing a database or spec sheet. This is especially useful during high-volume packing operations where the wrong box grade could compromise product safety.

Specifying Certificate Requirements

When you work with President Container Group, your desired strength rating and board construction are established during the quoting process. Whether you need ECT-rated or Mullen-rated board, the correct values will be printed on every box in every production run. Each design is assigned a unique specification number that ties the certificate stamp details to the complete engineering record for your packaging.

Our quality control team verifies certificate stamp accuracy as part of routine production checks, and our Box Compression Testing confirms that finished boxes meet or exceed the performance indicated on the stamp.