What Is an 8D, and How Do You Answer a Customer's 8D Request?

An 8D is a structured corrective action report, built on eight problem-solving disciplines, that a customer requests when your product fails a requirement. To answer one, contain the problem first, confirm the customer's facts, prove why the defect was made and why it escaped, then show evidence that the fix worked.

The form itself is easy to fill in. The hard part is that a customer quality engineer will read it looking for the sentence that doesn't hold up. This guide follows a customer complaint from the hour the request lands to the day the 8D closes, for quality engineers at suppliers who answer to OEMs.

Where does the 8D come from?

The method was developed at Ford, and its manual, Team Oriented Problem Solving, is dated to 1987. It has since spread well beyond automotive. Aerospace has its own version of the requirements in AS13000, and you will meet it in electronics and medical device supply chains too.

"8D" names both a method and a document. When a customer asks for an 8D, they usually mean their template, filled in and returned by a date. Learn the method, then write in their format.

What are the eight disciplines?

Labels vary by customer, and many forms add a D0 in front. Compare a few supplier manuals and you will see different names for D5 through D7. The substance is consistent:

D0, Prepare and respond. Emergency actions before the formal work starts. Not on every form.
D1, Build the team. People who know the product and the process. An 8D staffed only by quality is a common weakness.
D2, Describe the problem. What is wrong, against which requirement, how many, which lots. In measurable terms, with no cause in it.
D3, Contain it. Protect the customer while you investigate.
D4, Find and verify the root cause. Why the defect was made, and why it escaped.
D5, Choose permanent corrective actions. Actions that remove those causes, with evidence they should work before you roll them out.
D6, Implement and validate. Put the actions in place and prove the result in production.
D7, Prevent recurrence. Change the systems behind the failure and carry the lesson to similar parts and processes.
D8, Close and recognize the team. Confirm the actions are complete and share what was learned.

How long do you have to answer an 8D?

There is no universal deadline. The clock comes from the customer's supplier quality manual, the request itself or your contract, so find it before anything else.

Published examples show the range. One bus manufacturer's 8D form, filed with NHTSA, asks for a first response within 24 hours, a solution within 5 days and a verified corrective action within 15 days. A defense contractor's corrective action template allows 7 days for containment and typically 30 for the root cause and corrective action plan.

If you can't verify the fix by the due date, say so early. Send the containment, send the current state of the investigation, and ask for an extension with a reason before the date passes. A late 8D can count against you on the customer's scorecard even when the engineering turns out to be right.

What should you do in the first 24 hours?

Confirm receipt and name one owner. The customer needs a person to call.
Find the template and the dates. If you are certified to IATF 16949, clause 10.2.3 expects you to use a customer's prescribed problem-solving process unless the customer agrees otherwise.
Contain everywhere suspect product can be. Your storage, work in process, outside processors, shipments in transit and stock at the customer's plant. Containment that stops at your own door is the first thing a reviewer looks for.
Define the clean point. State the first lot, date or serial number you can certify, and how the customer can recognize certified stock when it arrives.
Preserve the evidence. Save process data before it is overwritten. Keep retained samples. Record the state of the tool and the setup before anyone adjusts them.
Ask for the returned parts and the customer's data. Photos, the conditions at failure, where in the line it was found, and how many were checked to find the bad ones.

How do you write a D2 problem statement a customer will accept?

Write what is wrong, with numbers, and leave the cause out. Here is an invented example.

Weak: Customer reports bad connectors.
Stronger: Customer found 14 of 1,200 connector housings from lots 4471 and 4472 with a cracked retention latch at line-side assembly on 6 October. The drawing allows no cracks.

Then add what is not affected. Which lots, lines, shifts, cavities and part numbers show the defect, and which comparable ones don't? This is the cheapest evidence you will gather all week, because whatever caused the defect has to explain that boundary.

What if you can't reproduce the defect?

Say so, and list the tests you ran. "No fault found" with nothing behind it reads as a refusal to look. Ask about the conditions at the customer's plant, compare process data for the affected lots against clean ones, and keep containment in place until the customer agrees it can come off.

Why does D4 need two root causes?

Because two things went wrong. Something in your process made the defect, and something in your controls let it leave. An escape point is the earliest control after the root cause that should have caught the problem and didn't.

Fixing only the first leaves a gap that the next, different defect can walk through. Fixing only the second means you keep making scrap and catching it. Many customer forms have separate lines for the two. If yours has one box, write both and label them. Our guide to aerospace CARs works through the distinction in more depth.

How do you prove a root cause instead of asserting it?

A candidate cause earns the name when it explains the boundary in your D2: why these lots and not the others. The strongest proof is turning the defect on and off by changing that one condition. Comparing good lots against bad ones is the next best thing.

Record the candidates you ruled out and the data that ruled them out. It shows the reviewer the work, and it stops the next engineer from starting over. A parameter being in spec doesn't clear it, since several in-spec conditions can align to produce a failure.

Is "operator error" an acceptable root cause?

Rarely. A person doing the wrong thing is where the question starts: what about the task, tooling, instructions or schedule made that the likely outcome? Retraining as the only action is a signal to the reviewer that the investigation stopped early, and we looked at why it tends to recur in The Recurrence Problem.

What do customers look for in D5 and D6?

In D5, they want to match each action to a cause. One action per cause at minimum, covering both made and escaped, each with an owner, a date and an effectivity point: the first lot or serial number built with the fix.

In D6, they want results measured the same way as the problem. Show before and after on the same characteristic, and for an escape fix, show that the new check catches known-bad parts.

Watch the length of your verification window on intermittent defects. If a failure shows up about every four months, a 90-day check with no recurrence passes about 47% of the time even when the fix did nothing. Size the window to how often the failure really appears, and say why you chose it.

What belongs in D7?

D7 is easy to fill with one sentence, and that sentence is usually "lessons shared." Better evidence looks like this:

The PFMEA, control plan and work instructions that changed, with revision numbers.
The similar parts, lines and plants you checked for the same condition, and what you found.
Past 8Ds you searched for this cause. If it has appeared before, say so and explain why the earlier fix didn't hold.

What makes a customer reject an 8D?

The root cause restates the symptom.
The root cause is a person, and the action is retraining.
There is one root cause and no explanation of the escape.
Containment covers your plant but not transit or the customer's stock.
Inspection is offered as the permanent fix.
Actions have no dates, no owners or no effectivity point.
Verification is an assertion with no data attached.
The cause matches a previous 8D that was closed as solved.

What if the cause sits with your own supplier?

You still own the answer to your customer. Ask the supplier for its 8D and data, review them to the same standard yours will be held to, and attach the evidence. Your incoming checks may also be part of the escape, so "supplier issue" doesn't finish D4.

How does Lattice help with 8Ds?

Lattice is AI investigation software for quality teams. It investigates a customer complaint from your own records and fills your OEM's 8D, in your OEM's template, with a source on every line. Your engineer reviews and signs. The aim is an 8D answered in days, with up to 80% of the hours back. See how it works for suppliers to automotive OEMs.

Sources

Lockheed Martin UK Ampthill (February 2025), Root Cause Corrective Action Problem Solving Guidebook, Issue 2. Origin at Ford, team composition, D0 to D8.
Wikipedia, Eight disciplines problem solving. Date of the Ford manual, D0, definition of an escape point.
SAE International, AS13000: Problem Solving Requirements for Suppliers, listing via Intertek Inform.
Blue Bird, Corrective Action Report (8D) form, filed with NHTSA (2023). Response deadlines printed on the form.
L3Harris, supplier corrective action request example. Containment and root cause deadlines, scorecard effects.
Auxiliary Machines (2026), The Recurrence Problem. Effectiveness check model.