Non-resident tax deduction certificates require assessment of chargeability, proportionate income determination, and limited validity. A payer seeking determination of the appropriate proportion of a sum, other than salary, payable to a non-resident and chargeable in the hands of the recipient must apply in the prescribed form. The Assessing Officer must examine chargeability under the Act and the applicable Double Taxation Avoidance Agreement, determine the proportion chargeable where only part of the sum is taxable, and issue a certificate for tax deduction. The certificate is valid only for the named non-resident and specified period, subject to cancellation, and a fresh certificate may be sought before or after expiry.