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Strategic Cost Management · Quality Cost Management

Cost of Quality: Prevention, Appraisal and Failure Costs

Updated 11 October 2026 · Fact-checked

Cost of quality is the total cost of achieving and failing to achieve quality. The PAF model splits it into prevention, appraisal, internal failure and external failure costs. To solve a question, tag each item with the right category, total each group, then compare conformance and non-conformance costs.

Understand Cost of Quality: Prevention, Appraisal, Failure Costs

Quality is not free. A firm spends money to make good products, and it also loses money when products turn out bad. Cost of quality (COQ) adds up both. The idea is to see the full bill so management can decide where to spend.

The PAF model has four categories. Prevention costs are spent to stop defects from happening: training, quality planning, supplier evaluation, preventive maintenance, process design. Appraisal costs are spent to find defects that already exist: inspection, testing, quality audits, testing equipment upkeep.

Internal failure costs arise when a defect is found before the product reaches the customer: scrap, rework, re-inspection, downtime due to defects, retesting. External failure costs arise when the defect is found after delivery: warranty claims, returns, product recalls, complaint handling, replacement, product liability, and lost goodwill and sales.

Prevention and appraisal together are the cost of conformance (money spent to make the product conform to specification). Internal and external failure together are the cost of non-conformance (money lost because it did not conform). Spending more on prevention usually reduces failure costs, often by more than the extra spend.

The key test for classification is timing and purpose. Ask: was the money spent to stop a defect, to find a defect, or because a defect was already found? If found, was it before or after the customer received the product?

Key rules to remember

Cost of conformance
Cost of conformance = Prevention costs + Appraisal costs
Voluntary spending to achieve quality.
Cost of non-conformance
Cost of non-conformance = Internal failure costs + External failure costs
Loss caused by failing to meet specification.
Total cost of quality
COQ = Prevention + Appraisal + Internal failure + External failure
Equals conformance plus non-conformance costs.
COQ as a percentage of sales
COQ % = (Total COQ ÷ Sales) × 100
Used to compare periods or units. Cost of each category can be shown the same way.
Classification test
Stop defect = Prevention; Find defect = Appraisal; Defect found before delivery = Internal failure; Defect found after delivery = External failure
Use this to tag every item.

How to solve Cost of Quality: Prevention, Appraisal, Failure Costs questions

Use this method for any classification or computation question on cost of quality.

  1. 1List every cost item given in the question and ignore items that are not quality related, such as normal production cost.
  2. 2Tag each item using the test: stops defects (prevention), detects defects (appraisal), defect found before delivery (internal failure), defect found after delivery (external failure).
  3. 3Total each of the four categories separately.
  4. 4Add prevention and appraisal for cost of conformance, and the two failure categories for cost of non-conformance.
  5. 5Add all four to get the total cost of quality, and express it as a percentage of sales if asked.
  6. 6Compare periods or options: note which category rose or fell and what that implies.
  7. 7Write a short conclusion that advises management, for example to raise prevention spend if failure costs are high.
  8. 8Show the working in a neat table-style list so the examiner can award marks for each category.

Quickest way: Four-bucket tagging

When to use it: Use when you have a long list of costs and limited time, mostly in MCQs and the first part of a numerical.

  1. Write P, A, IF, EF beside each item as you read it.
  2. Look for keywords: training, planning, design means P; inspection, testing, audit means A; scrap, rework means IF; warranty, returns, recall, complaints means EF.
  3. Add the four buckets, then check that their sum equals the sum of all quality items.
  4. Compute conformance and non-conformance only if the question asks.

Common mistakes in Cost of Quality: Prevention, Appraisal, Failure Costs

  • Treating inspection of incoming material as prevention.

    Inspection sounds like a way to stop problems.

    Fix: Inspection and testing find defects, so they are appraisal. Prevention is action taken before or in design of the process.

  • Putting rework in appraisal or external failure.

    Students confuse rework with re-inspection and with customer returns.

    Fix: Rework of defects found before dispatch is internal failure. Only defects found after delivery are external failure.

  • Ignoring lost sales and goodwill as an external failure cost.

    They are not in the accounting records, so they seem optional.

    Fix: Mention them as hidden external failure costs. Include a figure only if the question gives one.

  • Mixing up conformance and non-conformance.

    The terms sound alike.

    Fix: Conformance is what you spend to get quality (prevention plus appraisal). Non-conformance is what you lose through defects (failure costs).

  • Including normal production cost or scrap within normal loss as quality cost without reading the question.

    Students tag every cost that sounds like waste.

    Fix: Include only items the question links to quality. Follow any instruction on how normal loss is treated.

Worked examples

Example 1

A company reports these costs for a month: quality training ₹40,000; incoming material inspection ₹60,000; scrap ₹90,000; rework ₹50,000; warranty claims ₹1,20,000; supplier evaluation ₹30,000; customer complaint handling ₹40,000; final product testing ₹70,000. Classify the costs and find the cost of conformance, cost of non-conformance and total cost of quality.

Show the solution
  1. Prevention: training ₹40,000 + supplier evaluation ₹30,000 = ₹70,000.
  2. Appraisal: incoming inspection ₹60,000 + final testing ₹70,000 = ₹1,30,000.
  3. Internal failure: scrap ₹90,000 + rework ₹50,000 = ₹1,40,000.
  4. External failure: warranty ₹1,20,000 + complaint handling ₹40,000 = ₹1,60,000.
  5. Cost of conformance = ₹70,000 + ₹1,30,000 = ₹2,00,000.
  6. Cost of non-conformance = ₹1,40,000 + ₹1,60,000 = ₹3,00,000.
  7. Total COQ = ₹2,00,000 + ₹3,00,000 = ₹5,00,000.

Answer: Prevention ₹70,000; appraisal ₹1,30,000; internal failure ₹1,40,000; external failure ₹1,60,000. Conformance ₹2,00,000; non-conformance ₹3,00,000; total COQ ₹5,00,000.

Example 2

Sales were ₹50,00,000 in Year 1 and ₹50,00,000 in Year 2. Quality costs in Year 1: prevention ₹1,00,000, appraisal ₹2,00,000, internal failure ₹3,00,000, external failure ₹4,00,000. In Year 2: prevention ₹3,00,000, appraisal ₹2,00,000, internal failure ₹1,50,000, external failure ₹1,50,000. Compute COQ as a percentage of sales for both years and comment.

Show the solution
  1. Year 1 total COQ = 1,00,000 + 2,00,000 + 3,00,000 + 4,00,000 = ₹10,00,000.
  2. Year 1 COQ % = 10,00,000 ÷ 50,00,000 × 100 = 20%.
  3. Year 2 total COQ = 3,00,000 + 2,00,000 + 1,50,000 + 1,50,000 = ₹8,00,000.
  4. Year 2 COQ % = 8,00,000 ÷ 50,00,000 × 100 = 16%.
  5. Prevention rose by ₹2,00,000. Failure costs fell from ₹7,00,000 to ₹3,00,000, a fall of ₹4,00,000.
  6. Net saving = ₹4,00,000 − ₹2,00,000 = ₹2,00,000, which equals the fall in total COQ from ₹10,00,000 to ₹8,00,000.

Answer: COQ was 20% of sales in Year 1 and 16% in Year 2. The extra ₹2,00,000 spent on prevention cut failure costs by ₹4,00,000, so total quality cost fell by ₹2,00,000. The shift towards prevention was worthwhile.

Exam tips

  • In MCQs, decide the category by timing: before delivery is internal failure, after delivery is external failure.
  • In numericals, show each category total separately before the grand total. Marks are given for the classification.
  • Always add a one-line comment, such as the need to increase prevention spend when failure costs dominate.
  • Expect questions that pair this topic with cost reporting and optimum quality level, so be ready to read a COQ statement and draw a conclusion.
  • Learn two or three examples per category by heart for theory answers.

Practice questions from Quality Cost Management

Cost of Quality: Prevention, Appraisal, Failure Costs: frequently asked questions

What are the four categories of cost of quality?

They are prevention, appraisal, internal failure and external failure costs. This is the PAF model. Prevention and appraisal are spent to achieve quality, while the two failure costs arise from defects.

What is the difference between internal failure and external failure cost?

Both come from defective products. Internal failure cost arises when the defect is found before the product reaches the customer, such as scrap and rework. External failure cost arises when it is found after delivery, such as warranty claims, returns and recalls.

What is cost of conformance versus cost of non-conformance?

Cost of conformance is prevention plus appraisal cost, spent to make products meet specification. Cost of non-conformance is internal plus external failure cost, the loss from products that do not meet it.

Is inspection a prevention cost or an appraisal cost?

Inspection is an appraisal cost because it detects defects that already exist. Prevention covers activities that stop defects from occurring, like training, process design and preventive maintenance.