Section 80c is attracted where there is any payment for the propose of purchase or construction of a residential house property, the income from which is chargeable to tax under the head "Income from house property". In case the house in under construction, no income can be earned to be chargeable under "Income from house property". Therefore, no deduction of principal repayment of housing loan will be allowable u/s 80c in case the house is under construction.