Prepare cash book
Nov4. Received cheque from Mohan ₹1000 after allowing him discount ₹30
Nov9. Deposited mohan cheque into bank
Nov19. Mohan cheque returned by bank

Pragya, we believe that, your this doubt is related to Double Column Cash Book (with Cash and Bank Columns). 
Thus, the solution to your query is here. 

Cash Book
Dr.											Cr.
Date		Particulars	L.F.	Cash (Rs)	Bank (Rs)	Date	Particulars	L.F.	Cash (Rs)	Bank (Rs)
Nov. 09		Cheques-in-Hand A/c			1,000	Nov. 19	Mohan			1,000

Working Note:

Journal Proper
Date	Particulars		L.F.	Debit Amount (Rs)	Credit Amount (Rs)
Nov. 04	Cheques-in-Hand A/c	Dr.		1,000
	Discount Allowed A/c	Dr.		30
	To Mohan				1,030

However, if you still find any difficulty, then do get back to us. We will help you in the best possible way.