Why the rate has to sit on the item
GST is twice the nuisance in the material trade because a single invoice spans several slabs. Cement is 28%, TMT steel and most hardware 18%, sand and aggregate 5%. A billing system that asks for one GST rate per bill cannot produce a correct invoice for a contractor buying all three, which is most days. Holding the rate on the item — set once, alongside its HSN code — means every line takes its own and the totals split into CGST and SGST correctly without anybody thinking about tax while a customer waits.
Within the state and outside it
A sale inside your own state splits into CGST and SGST. To a buyer in another state it becomes IGST at the combined rate, and getting that wrong is a filing problem rather than a rounding one. The buyer's state comes from the party record, so the treatment switches automatically and the correct state code prints on the invoice. For an inter-state despatch the vehicle and freight details are held alongside, which is what the e-way bill portal asks for.
HSN codes, once
The HSN code is what your return actually reports against, and a wrong one surfaces during scrutiny rather than at the counter. The common material codes are stable — 2523 for cement, 7213 and 7214 for TMT and structural steel, 2517 for aggregate, 6907 for tiles, 7318 for fasteners. Set the code against the item when you create it, with our team's help during setup for anything you are unsure of, and it appears on every bill afterwards without further thought.
What your accountant receives
At month end the GSTR-1 and GSTR-3B summaries come out already grouped the way the return needs them: B2B separated from B2C, credit and debit notes listed, an HSN summary built from the item records, tax broken down by rate, and input credit captured from your purchase entries. Your CA works from that instead of turning over the bill book to rebuild figures that already existed. The three days most shops lose to this every month is the single largest saving in the software.