OnlineVFR uses graphics to explain when a pilot is required to readback information from a controller.
Readback requirements
TAGS
Readback Altimeter setting | Readback Approach instructions | Readback Backtrack | Readback Basic or traffic service | Readback Circuit direction | Readback Cross active runway | Readback Frequency change | Readback Heading change | Readback Holding point | Readback Level instructions | Readback requirements | Readback Runway clearance | Readback Runway in use | Readback speed | Readback taxi instructions | Readback transponder squawk