Transfer of amount from NRO to NRE account on sale of property

A.MISHRA (professional) (91 Points)

01 February 2019  
Dear sir,

I am a NRI , having a residential house in kolkata (India) which has been acquired under the operation of law( Inherited property).

In the last week I sold the same property for an amount of 25laks (INR) and the money was received through a DD. Due to which i suffered a LONG TERM CAPITAL LOSS( considering acquisiton cost as zero or cost to previous owner).Also purchaser has not deducted any TDS on same payment.
Now I have to transfer the same amount in my NRE account.
I want to know is it taxable as per Income tax act,1961??? Will the CA will identify it as taxable in india while certifying in form 15CB.???

Is any exemption / releif under DTAA available against this transaction , if yes pls specify me the clause under which it is exempted or releif can be availed.
Is it mandatory to furnish certificate from CA in form 15CB in above case?????