How to write an A3 report: the 7 zones, step by step
The A3 is Toyota's one-page problem-solving report, named after the paper size. Done right, it tells your sponsor the entire story — problem, current condition, target, root cause, countermeasures, plan, and follow-up — in less than five minutes of reading.
Zone 1: Background
Why does this matter now? Strategic context in 2-3 sentences. Tie it to a business priority, a customer complaint, a compliance risk, or a growth target. If leadership can't tell why you're doing this, the rest of the A3 won't land.
Zone 2: Current condition
Facts, data, observations. What does today look like, in numbers? Include the primary metric baseline and the specific pattern (shift, line, time of day, SKU). A chart earns its space if it shows the problem at a glance.
Zone 3: Target condition
Measurable 'what good looks like.' A numeric target, a deadline, and a success criterion. 'Reduce scrap' is not a target. 'Cut Line 2 B-shift rejects from 7% to ≤2% by September 30, sustained 60 days' is.
Zone 4: Root cause analysis
A compressed fishbone or 5-Why summary. Don't list every hypothesis — list the confirmed root causes and the evidence that confirmed them. This is the most common zone reviewers push back on.
Zone 5: Countermeasures
Specific fixes, each tied to a named root cause. A countermeasure that doesn't tie to a cause is a wish list item. Include the top 2-4, not 15.
Zone 6: Implementation plan
Who, what, when. Every countermeasure has an owner and a due date. Milestones are explicit. A Gantt snippet belongs here.
Zone 7: Follow-up and sustainment
How will you verify the gain holds? Sustainment check cadence (30/60/90 day), leading indicators, and the reaction plan if drift appears. Reviewers who've seen gains evaporate will look here first.
Common A3 mistakes
- Too much text — A3 is a visual discipline, use diagrams and tables
- Zone 4 (root cause) with no evidence for the 'confirmed' causes
- Zone 5 (countermeasures) with fixes that don't tie to Zone 4 causes
- No Zone 7 — plans to sustain are what separate Six Sigma from Six Graveyard