Penalty for gstr 10

9 months back, GST Registration for the firm was cancelled. There is NIL liability for Final Return. However, due to delay in filing of GSTR 10, now it is showing Rs. 10,000 as penalty. No notice was received for filing of GSTR10. My query is:

1. Can penalty be levied for NIL returns

2. Can penalty be levied even without giving notice (read that 15 days notice is required)

3. What is better course of action? Should one pay penalty and close or wait for notice?