A supplier investigation depends on a factual observation record you control. The point is not to assign blame in the first report. It is to give the supplier a compact packet they can use to reproduce, test, and trace the issue. This article shows the exact elements to collect, how to present them, and how to use the record to get a meaningful supplier response.

Start with the minimum investigative facts

Begin the record with five immutable facts: item identification, where the item was found, the inspection or discovery date, the lot or serial numbers, and the quantity affected. These anchor the investigation to production and logistics events the supplier can trace.

Add source context: whether the sample came from a pre-shipment inspection, returned customer unit, incoming container, or in-line QA. State who handled the sample and whether it has been stored or altered since discovery. If a sample has been cleaned, cut, or otherwise changed record that explicitly.

• Item code and description (SKU, color, model)
• Location found (warehouse, customer address, shipment stage)
• Date and time of discovery
• Lot, batch, or serial numbers
• Quantity affected and sample IDs

Describe the defect in concrete, repeatable terms

Use objective language focused on observable attributes. Replace terms like poor, defective, or bad with measurable descriptions: crack length, peel length, discoloration Delta value, hole diameter, missing component, loose stitching count, or electrical open circuit. Give units and a tolerance where possible.

Include the exact test or method used to observe the defect. If you measured a peel force, state the instrument model and settings. If you used a visual comparator or a specific standard, name it. This lets the supplier repeat your observation without guessing the method.

• Quantify. Example: 'peel separation at seam: 12 mm, perpendicular to edge'
• Specify instrument or method: 'measured with digital caliper, resolution 0.01 mm'
• State pass/fail criteria referencing drawing or spec

Photograph and label evidence so the defect is obvious

Good photos reduce back-and-forth. Take multiple images: a context shot showing where the sample came from, a close-up of the defect, and a scale reference. Use a neutral background and consistent lighting. Include a ruler or a marked scale in each close-up image to show size.

Annotate each image and tie it to a sample ID and a line in your written record. Number images and add short captions that describe the view and what the supplier should focus on. If a defect is internal, a cross-section photo or X-ray image may be necessary; label the cut location and orientation.

• Context, close-up, scale reference
• Consistent lighting and neutral background
• Image file name = sampleID_view_number (for example: SKU123_sampleA_close1.jpg)

Compare the observation to the spec or drawing

State exactly which specification, drawing, measurement tolerance, or test method the item is failing against. Quote the clause, dimension, or acceptance criteria. If the supplier produced the drawing, reference its revision and date. If no formal spec exists, document your internal acceptance criteria.

If the observed condition lies near a tolerance boundary, show the math. Present the measured value, the allowed range, and whether the point is a solid fail or a borderline case. This prevents argument about whether the issue is outside the contract requirements.

• Reference: drawing number, revision, and clause
• Measured value versus allowed tolerance
• Indicate borderline results explicitly

Ask the supplier for containment and an investigation plan

Use the record to request two actions: immediate containment to prevent further shipments of affected units and a corrective action plan to investigate cause and prevent recurrence. Be specific about the containment you expect. For example: hold the remaining batch in quarantine, stop shipment of outgoing containers with the same lot number, or segregate production line output pending review.

Require a timeline and deliverables: initial acknowledgment, source inspection report, root cause analysis, proposed corrective actions, and verification activities. Ask for photographic evidence of containment and for samples returned if needed. Set a reasonable deadline so the supplier prioritizes the task.

• Containment request example: 'Quarantine lot 4523; do not ship. Photograph quarantine location within 24 hours.'
• Investigation deliverables: acknowledgment, cause analysis, corrective action, verification date

Use the record to make the next sourcing decision

Translate the supplier response into a decision record. For each possible outcome, accept with price adjustment, rework, reject and recall, or request corrective production, capture the evidence the supplier submitted, the timeline, and the verification steps. Record who approved each decision and on what factual basis.

If technical testing, material analysis, or third-party lab work is needed to settle a dispute, state that in the decision record and request a timeline and cost estimate. Recognize when a qualified specialist such as a materials engineer or testing laboratory should evaluate samples; the decision to hire one depends on technical complexity and commercial stakes.

• Decision record should include supplier evidence, verification method, responsible approver, and deadline
• Note when external testing or specialist input is required

Attach this observation record to the supplier inquiry and request acknowledgment within 48 hours.