I am GST registrant but NOT SST registrant.
I issue a tax invoice as security deposit (rental of machinery) to customer RM10,600 (incl GST) on November 2017, but this year on October 2018 my customer stop rent the machinery and they want use this deposit to cover the debt on September 2018 invoice which is RM10,000. Our debtor account will hang on a balance which is RM600. How should i do? Should i issue credit note? What is the treatment for credit note?