Carry forward of business loss permitted on re-establishment, with set off against business profits and extended carry forward. A proviso allows losses from a business discontinued under the discontinuance provision that is re-established within the revival period to be carried forward to the assessment year of re-establishment, set off first against that business's or any other business's profits for that year, and if not wholly set off and the business continues, carried forward for a limited number of succeeding assessment years; the general non-set off rule is amended to exclude these losses.