• Has the Company been established an official working language?
• Is all crew on-board able to communicate effectively in working language?
• Is ship's working language being recorded in Bridge Log Book?
• Are all posted plans and lists being written in ship's working language?
• Is English language used for communications related to navigation?
• Are IMO standard marine communication phrases used during navigation? 

References

IMO, International Convention for the Safety Of Life At Sea (SOLAS)

IMO, Standard Marine Communication Phrases. Resolution A.918(22). Available at: https://wwwcdn.imo.org/localresources/en/OurWork/Safety/Documents/A.918(22).pdf 

IMO, SMCP IMO Standard Marine Communication Phrases. Publication.

OCIMF, SIRE 2.0

Rightship, Ship Inspection Questionnaire