Income from a foreign transaction

Hello,

I got a simple query. I am acting as a commission agent in international trading. The buyer is in Korea and the seller is in South Africa. I'm the intermediary. The seller has fixed my compensation and the buyer has signed the ncnda so that my commission is secured. The deal is about to take place and I'm sitting in India. Ncnda has my account number. I hold that account in my bank in India. The money would get transferred to my account as soon as the ncnda is endorsed by the banks after the deal. 

The transaction's happening in USD, and I'm paid in USD. I'm I still liable to pay the tax? The among is USD 20000.

Please let me know.

thanks.