Four Ds
TfL's 2022 booklet says that once you have four D grades on a stage, you start that stage again, regardless of the points you had built up. TfL's web page puts it more loosely: too many Ds and you may be put back to a previous stage.
Repeated failure at Stage 3
TfL's policy says an All London candidate who keeps failing Stage 3 goes back to the Stage 2 written exam. A Suburban candidate may take Stage 3 twice; after a second failure there is a six-month wait, and after two more failures TfL considers refusing the application.
The U grade
If illness or something else outside your control means you cannot be tested fairly, tell the examiner, ideally before you start. One U, for untested, is allowed on each stage and does not count towards your Ds.
Appealing
A decision to make you repeat a stage can be appealed to TfL's Head of Driver Assessment, and then to the Taxi and Private Hire General Manager.
Sources
- TfL, Introduction to the Knowledge of London, March 2022, pages 14 and 15, Appendix A
- TfL, Taxi and private hire driver policy, version 6.0, 1 September 2026, section 3.11.1
From the guide: Knowledge appearances, and how they are marked