Tax deduction at source requires specified government purchasers to withhold tax, remit timely, issue certificates, and enable credit. Section 51 authorises the Government to require specified public entities and notified persons to deduct tax at source from payments to suppliers exceeding a prescribed contract value, excluding tax components from the deductible base and providing an exception for supplies located outside the State of recipient registration. Deducted tax must be remitted monthly in the prescribed manner; the deductor must issue a certificate to the supplier detailing contract value, deduction and remittance; failure to issue the certificate incurs a capped daily late fee. The deductee may claim credit in its electronic cash ledger; interest and default determination and refund rules apply under the Act.