Tax exemption

I think you can claim deduction based on certificate issued by the financer. Also risk will be on shoulder of client. Lets see other's view also.

Interest paid during the construction period is "Pre-Construction Interest" which can be claimed only  from the year in which construction has been completed.In your case as construction is not completed no chance to get Interest deduction under the head "Income from House property" and one of the pre condition to tax an income under this head is there should be some Building(Super structure) to land appuarent to ,so unless you construct house,you can not claim benifit under this section.If you construct you can claim it.

you can not claim interest on loan taken for land purchase.

Because we can cliam interest for only building or land appartuenant thereto which is self occupied.

but in your case there is no building which is self occupied.

Thanks to all for your replies