What do line umpires call, and what does the chair umpire call?

Under Appendix VII of the 2026 ITF Rules of Tennis:

• Line umpires and net umpires, where assigned, make all calls relating to their line or the net, including foot faults on their line.
• The chair umpire calls any line (including foot faults) or the net where no line or net umpire is assigned, and has the right to overrule a line or net umpire when sure a clear mistake has been made.
• The chair umpire may stop or suspend play whenever necessary, and makes decisions on continuous play and coaching under whichever approved Code of Conduct is in operation.