Works contract billing
One contract, one service, one rate
Under GST, a works contract for immovable property is a supply of services, so the whole contract is billed as one service at one rate. The law expects separate accounts for each contract.
In TallyPrime, you bill the contract from a service ledger set up with its GST rate and SAC. Once saved, the invoice appears in GSTR-1 and GSTR-3B, ready for filing.
Every contract is billed and reported the same way, however many run.