Assessment under section 143(3)

9 months from the end of the FINANCIAL YEAR in which return was filed.

For Resident 21 months from the end of relevent assement year.

For Transfer pricing 33 months from the end of relevant assessment year

I think it is 9 months from the end of month in which return is filed.

Assessment orders under section 143(3) of The Income Tax Act, 1961  have to be   made within 21 months from the end of the relevent assessment year as per section 153(1)(a) of The Income Tax Act,1961.