READING NOTE · UPDATED 2026
An A3 starts with an observed gap
The short original A3 introduction is accompanied by a current worksheet and a full worked procedure. Start with the difference between the expected and observed condition. Keep a proposed cause separate from evidence. A compact document should support a conversation with the people doing the work, not merely fit a problem into a fixed template.
A practical next step
- Describe the gap with a dated observation.
- Write a hypothesis that could be disproved.
- Use the worksheet to assign one test and review date.
This 2026 reading note is written by the Durnall editorial team. Richard Durnall’s original text follows below.
Read the diagram as text
Describe the current condition, define the gap, investigate a possible cause, choose a countermeasure, plan a test and review the evidence. Keep observations distinct from hypotheses.
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The original words below retain their period and attribution. The reading note above is the current editorial addition.
Source capture · 2013-01-14 ↗A3 reports have been a favourite Lean tool of mine for a long time. The idea is a simple one… All reports should be presented on a single side of a single piece of A3 paper. The philosophy is that ‘less is more’, all the information required should be concise, anything else is just fluff.
Toyota have been applying this concept for a long time and I’ve seen it successfully adopted at a number of organisations outside of Toyota. I heard a rumour about a year ago that Toyota are moving to A4 reporting but I’m not sure in the truth behind that one.
To understand the power that this simple tool provides sit down and think about the amount of time you spend writing stuff and reading stuff. Will anyone read past the executive summary of your business case? Will your executive come back to you and say “that report’s great but could you summarise it to me in a paragraph?”. Maybe A3′s are worth a shot.