First of all you need to take GST registration, TAN registration for TDS deduction u/s 195 in the given case. For any business related payments by individual, proprietor need to register themselves under TAN for TDS deduction u/s 195. TDS rate shall be ranging from 10.4% to 10.92% depending upon the transaction value per payee in a year (rate changed due to surcharge rate, whereas base rate remain constant i.e. 10%) or the rate prescribed under DTAA whichever is lower. You also need to file TDS return on quarterly basis and issue TDS certificates through TRACES if payee has PAN registered in India. If payee doesn't have PAN registered in India, prepare a manual TDS certificate and share it with payee for WHT credit in their resident country.
In case DTAA is silent on TDS rate on FTS, please check whether any other close nature of transaction to FTS has been covered under respective DTAA and deduct TDS accordingly. Generally, tax office is very aggressive on TDS compliance and hence, any non deduction of TDS just because TDS rate not defined under DTAA shall trigger litigation point and tax office may jump on the same with all provisions. Hence looking at the TDS amount and cost of litigation if tax office issued negative order, it is always advisable to deduct TDS in such case to be on safer note. If it's a bigger order, you can always take CA's advice on applicability of WHT provision.
Regards,
Manoj