Determination of withholding tax on payments to non-residents via Form 15E establishes the taxable proportion and TDS basis. Form 15E is an application under section 195 to obtain a certificate fixing the appropriate proportion of non-salary sums payable to a non-resident chargeable to tax; it requires payer and recipient particulars, full transaction description (nature of payment), taxability analysis under domestic law and under any applicable DTAA with justification and proposed TDS rate, and specified supporting documents including Tax Residency Certificate and Form 10F, concluding with a verified declaration by the applicant.