Student or Learner
I'd like to know if this sentence is correct:
You can pay by cash or cheque.
I am not a teacher.
I wouldn't say that myself.
You can 'pay cash', or 'pay in cash', or 'pay with cash' but not 'pay by cash'. You can 'pay by cheque' though, so it would sound better to say, "You can pay by cheque or cash."
You can pay with cash or cheque would work too.
You can certainly "pay by cash" in AusE.
Here too. "You can pay by cash or check" is a very normal phrase.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.