Tax deduction at source mandated on specified government payments, with prescribed payment, certification, ledger credit and refund procedures. Section 51 requires specified government entities and notified persons to deduct tax at source on supplies above the monetary threshold, except where supplier location and place of supply differ from the recipient's State or Union territory of registration; it prescribes that deducted amounts be paid to Government within ten days after the month-end, that the deductor furnish a certificate to the deductee with contract and deduction particulars, that the deductee claim credit in the electronic cash ledger, that interest apply for non-payment, and that defaults, refunds and excess deductions be handled under the Act's existing provisions.