GST transition guidance clarifies tax treatment for goods, services and works contracts and invoicing requirements. Guidelines set transitional tax rules for pre GST and post GST contracts by state entities covering goods-only, services-only and mixed works contract supplies. VAT or service tax continues to apply for supplies and invoices predating GST, subject to invoice timing rules (thirty day invoice window for services and works contracts), while GST applies where supply or invoice occur on or after GST commencement. Taxable value under GST must be computed so total billed amount inclusive of CGST and SGST does not exceed the pre GST contract price. TDS under GST is not to be deducted until the statutory provision is notified.