Section 139(3)

"Can he set off the income (LOSS) against the income of same year if he does not file income with in the due date or in case a belated return is filed for AY 2018-2019"

Yes.

After making intra-head adjustment (if any) the next step is to make inter-head adjustment. If in any year, the taxpayer has incurred loss under one head of income and is having income under other head of income, then he can adjust the loss from one head against income from other head, E.g.,Loss under the head of house property to be adjusted against salary income.

Restrictions to be kept in mind while making inter-head adjustment of loss

Following restrictions should be kept in mind before making inter-head adjustment:

Before making inter-head adjustment, the taxpayer has to first make intra-head adjustment.
Loss from speculative business cannot be set off against any other income. However, non-speculative business loss can be set off against income from speculative business.
Loss under head "Capital gains" cannot be set off against income under other heads of income.
No loss can be set off against income from winnings from lotteries, crossword puzzles, race including horse race, card game, and any other game of any sort or from gambling or betting of any form or nature.
Loss from the business of owning and maintaining race horses cannot be set off against any other income.
Loss from business specified under section 35ADcannot be set off against any other income ( section 35AD is applicable in respect of certain specified businesses like setting up a cold chain facility, setting up and operating warehousing facility for storage of agricultural produce, developing and building housing projects, etc.)
Loss from business and profession cannot be set off against income chargeable to tax under the head "Salaries".