Calculating confidence score in NER
Named Entity Recognition is traditionally evaluated using precision/recall and F1 score [https://towardsdatascience.com/entity-level-evaluation-for-ner-task-c21fb3a8edf] - the medium article gives a low down on how to achieve this
I recently happened to read this article on a new approach for the same. Please see the details in the attached medium link : [https://towardsdatascience.com/a-pathbreaking-evaluation-technique-for-named-entity-recognition-ner-93da4406930c]  but havent tried this out yet though