Tax Deduction at Source under GST requires deductors to register, deposit via CPIN/CIN and file monthly returns. Section 51 requires government deductors to register on the GST portal, withhold TDS on taxable supplies above the statutory threshold, generate CPINs for deposits via NEFT/RTGS or OTC, obtain CIN credits to the electronic cash ledger, maintain a register (Annexure A), file monthly FORM GSTR-7 to enable credit to deductees, and issue FORM GSTR-7A TDS certificates. Two operational modes are prescribed: individual bill-wise CPIN generation and periodic bunching with Suspense Head aggregation.