The 'Loss of a Specified Business' referred to in section 35AD of any assessment year is allowed to be set off only against profit and gains, if any, of any other specified business. But if such loss of specified business has not been wholly set off, so much of the loss as is not so set off or the whole loss where the assessee has no income from any other specified business, shall, subject to the other provisions of this Chapter, be carried forward to the following assessment year, and—
it shall be set off against the profits and gains, if any, of any specified business carried on by him assesssable for that assessment year; and
if the loss cannot be wholly so set off, the amount of loss not so set off shall be carried forward to the following assessment year and so on.
In other words, loss of specified business can be carried forward indefinitely till it is set off.
Return of Loss should be Submitted in Time (Section 80) for Carry Forward and Set Off of Loss of Specified Business.
Loss under section 73A cannot be carried forward unless the return of loss has been furnished before the due date prescribed u/s 139(1).