In the current case, where Non Resident already has a PE in India, You must obtain the following documents for applying the DTAA Rates for Withholding Tax on Foreign Remittance.
- Tax Residency Certificate - Issued by the Tax Department of Country where Non Resident is
- Form 10F
- Copy of PAN Card (if available with the vendor)
As per the requirement of the Income Tax Act 1961/ RBI guidelines issued to Bankers, request for any foreign remittance to the Bank is required to be supported by a certificate from a Chartered Accountant (Form 15CB) certifying correct deduction of tax there on. Further details of the same is required to be filed online in the prescribed format (ie Form 15CA on website of Income Tax Deptt by applying digital signature of Managing Director.
Hope this clariies...