Return filing obligations require electronic periodic returns, payment by filing deadlines, and limited post filing rectification under GST. Most registered persons must furnish electronic returns reporting supplies, input tax credit and tax due for each tax period; composition taxpayers file quarterly while other categories (deductors at source, input service distributors, non-residents) follow specific timelines. The Commissioner may extend deadlines by notification. Tax due must be paid by the return filing date, returns are required even if no supplies occurred, post-filing rectifications are allowed (subject to interest and a statutory cut-off and except where errors are found by authorities), and filing is barred if prior period returns are outstanding.