Use the correct number on the scoreboard
Badminton BC’s governing-body rules overview places the singles server on the right for an even score and the left for an odd score. The relevant parity is the serving player’s score, not the receiver’s or the combined rally total.
At 8–7 with the player on eight serving, the right service court corresponds to the even eight. If the other player wins the rally and becomes server at eight-all, that new server also has an even score. A change of server does not automatically mean a change to the left court.
A parity check is smaller than a scoring-system check
This rule explains which side starts a serve; it does not establish the game’s winning target or every service-action requirement. Keep those questions separate when watching a match under an event-specific format.
For a viewing note, place a small right-or-left marker beside the current server’s score and update it after the rally. Using the receiver’s number will sometimes give the right answer by coincidence, then fail at a score where the parities differ. The 8–7 example exposes that coincidence without requiring a long simulated game.
Questions answered
Whose parity determines the singles service court?
The current server’s.
Does changing server automatically mean serving from the left?
No. Read the new server’s score.
Sources & further reading
Official references for the subjects discussed. Service terms and device software can change.