If you dont set off, you will end up paying more tax as as result of more taxable income.
Business loss can be carry forwarded only when there is no other income from any other head except salary.
That means business loss cant be forwarded if there is income under any other head(except salary).
And moreover if you carry forward a business loss, then such carry forwarded business loss can be set off only under that head and not under any other head whereas in current year you can setoff with anyother head except salary.
Why is that you wish to carry forward a loss when there is income? Any reason?.