set off

From speculative gain you can set off non speculative loss of current year. This is however not allowed the other way round. So there is no question regarding the same in any subsequent year either..

I assume that you have  non speculation loss in the current year and want to set off against speculation income of the current year.  You can do it. In fact, the question of carry forward and set off doesn't arise in your case because, only after current year's inter head set off under Section 70, the question of set off of carried forward loss arises.