Yes, it is mandatory to declare a 14-digit FSSAI License or Registration number on cash receipts/purchase invoices/cash memos/bills, etc. by all food businesses. When any operator issues 2 transaction documents such as issuing transport challan/ Bill etc and an invoice, then FSSAI number needs to be mentioned on both documents. The only exemption will be the GST e-way bill and such other govt documents which are system generated.