If your builder is demanding additional maintenance fees for a period you've already paid for and received a 'no dues' certificate, you likely don't need to pay. Once a society is formed and maintenance is handed over, the builder's right to charge typically ends. You have the right to scrutinise the builder's maintenance expenses and can complain to RERA if the builder violates the Real Estate (Regulation and Development) Act, 2016, especially concerning essential services and outgoings before possession transfer.