Tax deduction at source: mandated deduction from specified contract payments with prescribed payment, certificate, ledger credit and interest rules. A government-mandated withholding requires specified public entities or notified persons to deduct tax from supplier payments above a notified contract-value threshold, excluding invoice tax. Deductors must pay amounts to the appropriate government within ten days after month-end and provide the deductee a prescribed certificate stating contract value, deduction rate and amounts. Failure to issue the certificate attracts a capped daily late fee; failure to remit attracts interest and default procedures. Deductees claim credit in their electronic cash ledger as reflected in the deductor's return, and refunds of excess or erroneous deductions follow the prescribed refund procedure.