Return filing obligations require electronic submission and timely payment, with category-specific deadlines and limited rectification rights. Section 39 establishes category-specific electronic return filing obligations and timelines, requiring registered persons to report supplies, input tax credit, tax payable and tax paid; it mandates tax payment by the return due date, obliges filing for every tax period including nil periods, permits Commissioner-issued extensions, allows limited rectification of errors in subsequent returns subject to interest and a statutory cut-off, and bars filing new returns while prior-period returns remain outstanding.