Mandatory readbacks: what you must read back
Some ATC instructions can’t be answered with just “Roger” — you must repeat them back word-for-word so the controller knows you heard them correctly. Here is the standard list, and the difference between Roger, Wilco and a full readback.
The mandatory readback items
- Taxi and towing instructions
- Level instructions
- Heading instructions
- Speed instructions
- Airways or route clearances
- Approach clearances
- Runway-in-use
- Clearance to enter, land on, take off on, backtrack, cross or hold short of any active runway
- SSR (squawk) operating instructions
- Altimeter settings — including the units when the value is below 1000 hectopascals
- VDF information
- Frequency changes
- Type of ATS service
- Transition levels
CAP 413 Edition 24, §2.69. End the readback with your callsign. Information such as the wind, a readability report or traffic is acknowledged rather than read back.
A conditional clearance is read back with the condition FIRST and in the same sequence it was given — “behind the landing Cessna, line up runway two four, behind”. Read back complete and in order: an incomplete read-back is harder to spot than a wrong one.
Roger, Wilco — or a full readback?
Roger
“I have received all of your last transmission.”
Acknowledges information only. It does NOT mean you will comply, it is never used where a readback is required, and it is never the answer to a question — use “Affirm” or “Negative” for that.
Wilco
“Will comply” — I understand your message and will comply with it.
Use to acknowledge an instruction you will act on, e.g. after “report final” → “Wilco, G-ABCD.”
Report …
An instruction to tell the controller when you reach a point or condition, e.g. “report final”, “report field in sight”, “report downwind”.
Acknowledge it now — “Wilco, G-ABCD” (or read back the report point) — then actually make the report when you get there.
Readbacks are a habit, not a list
TowerTalk’s Exercise B drills readbacks against an AI controller with instant CAP 413-based feedback — free to try.
Related
Study aid, written in our own words from TowerTalk’s revision material (based on standard CAP 413 conventions). Last reviewed 3 July 2026; awaiting independent expert review. It does not reproduce CAP 413 and is not a substitute for it — always defer to CAP 413 and the current official publications, and to your instructor and examiner. TowerTalk is not CAA approved.