Tax deduction at source: mandated withholding from supplier payments with remittance, certification, credit, interest and refund rules. The provision allows the Government to mandate specified entities to deduct tax at source at a set rate from supplier payments above a threshold, excluding deduction where supplier location and place of supply differ from the recipient's State of registration and excluding specified taxes from the value. Deductors must remit withheld amounts monthly within a prescribed period and issue certificates to deductees; penalties apply for delayed certification. Deductees claim credit in their electronic cash ledger via the deductor's return. Interest and default determination follow existing interest and assessment provisions, and refunds are governed by the refund provision, subject to conditions where credit has been given to the deductee.