What Is Certificate of Conformance (CoC)?
Also known as: CoC, C of C, certificate of conformity, CofC, material certification
Definition
A certificate of conformance (CoC) is a document from the manufacturer or supplier, signed by an authorised person, stating that delivered goods or services meet the purchase order, drawing and specification requirements, with traceable lot or serial references.
Certificate of Conformance (CoC) Explained
A CoC typically states the part number and revision, quantity, purchase order number, applicable specifications and standards, lot, batch or serial numbers, date, and the name and signature of the quality representative. It is a statement of conformity, not test data. When actual test results are needed, for example chemical and mechanical properties of metal, a material test report or mill certificate (EN 10204 type 3.1 or 3.2) is requested in addition.
Receiving checks the CoC against the purchase order before material is accepted. Common reasons for rejection are a missing revision, quantity mismatch, absent signature, wrong specification callout, or lot numbers that do not match the packing slip. In aerospace and defence, purchase orders often add flow-down clauses requiring certificates for raw material, special processes (heat treat, plating, NDT) and approved sources, with counterfeit part prevention under AS5553 and AS6081 for electronic parts.
Trust varies by risk. For low risk commodity items, a CoC may be enough to release stock without inspection (certificate based or dock-to-stock acceptance). For critical items, buyers verify by sample inspection or independent testing, because a CoC is only as reliable as the supplier's quality system. Falsified certificates are a known fraud mode in metals and fasteners.
In ERP the CoC is attached to the receipt, lot or purchase order line as a document, and the lot number links the certificate to inventory and downstream job genealogy. SyteLine and LN support lot tracking and document attachments, and an AI document reader can extract fields from supplier PDFs and compare them to the PO before the inspector sees them.
Why It Matters
- Customer flow-downs and standards such as AS9100 require evidence that purchased product meets requirements, and the CoC is the usual record.
- A CoC tied to a lot number enables traceability from finished product back to material source during recalls and investigations.
- Checking certificates against the PO catches wrong grade, wrong revision and unapproved source before production starts.
- Counterfeit and falsified material risk is reduced when certificates are verified, not just filed.
In Practice
A purchase order for 500 AN fasteners requires material certification and a CoC. Receiving finds the CoC lists the right part number but the lot number on the box ends in 7 and the certificate says 1. The receipt is held, the supplier is asked for a corrected certificate, and the stock stays in quarantine in the ERP. Because the lot number was caught at receipt, traceability on the finished assembly stays intact.
Frequently Asked Questions
What is the difference between a CoC and a material test report?
A CoC states that product conforms to requirements. A material test report (mill cert) reports measured results like chemistry and strength, tied to a heat or lot number.
Who signs a certificate of conformance?
An authorised representative of the manufacturer or supplier, usually from quality, whose signature and title are on the certificate.
Can a CoC replace incoming inspection?
For low risk items under an approved supplier agreement, sometimes. For critical or safety related parts, buyers still inspect or test because a certificate is a claim, not proof.
How is a CoC stored in an ERP?
As an attachment on the purchase order receipt or lot record, linked by lot number so it can be retrieved with the job and shipment genealogy.
Related Terms
Traceability
Traceability is the ability to follow the history, location, and application of a part or material through the supply chain and production process, both backward to its sources and forward to every product and customer it reached.
Incoming Inspection (Receiving Inspection)
Incoming inspection, also called receiving inspection or IQC, verifies purchased material against the purchase order, drawing and specification before it is released to stock or production. Checks include documents, count, visual, dimensional and sometimes lab testing.
AS9100
AS9100 is the quality management system standard for the aviation, space, and defense industry, published by SAE and the International Aerospace Quality Group, which incorporates all of ISO 9001 and adds sector-specific requirements for safety, configuration, and risk.
AS5553 (Counterfeit Parts)
AS5553 is the SAE standard defining requirements for avoiding, detecting, mitigating, and disposing of counterfeit electrical, electronic, and electromechanical parts, used by aerospace and defense organizations to build a documented counterfeit parts control plan.
ITAR
ITAR (International Traffic in Arms Regulations) is the US State Department regulation, at 22 CFR Parts 120-130, that controls the export of defense articles, defense services, and related technical data listed on the United States Munitions List.
Go Deeper
SyteLine Receiving and Inspection Setup
Configure SyteLine receiving and quality inspection workflows. Set up PO receiving, inspection plans, and non-conformance triggers in CloudSuite Industrial ERP.
SyteLine Supplier Quality Management
Configure SyteLine supplier quality management for vendor quality scoring, incoming inspection tracking, and supplier corrective actions in CloudSuite Industrial.
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