Cancelled GSTIN

My client have a cancelled GST number on Sep19. And his last filed return is Feb19. Also he is having 2Lakhs of (SGST+CGST) lapsed ITC. I need experts review my opinion as
- Will I file Returns upto Sep19 with nil+reversal ITC. Because, If I filed properly, I needed to pay whole output tax with 18% and ITC reversal with 24%
- Suggest, Any other way to reduce burden.

Thanks