Urgent help required against computation of Taxable income

My uncle is doing a small Real Estate Construction Business. He has filed his IT Return as Proprietor U/S 44AD till F.Y. 2017-18 with closing stock of Rs. 35 Lakh. He is now doing a project with Mr. X under a joint agreement but without establishing any partnership firm. Is he allowed to file his IT return U/S 44AD as capacity of partner? If so then the proportionate sale amount should be shown or the gross sale value will be entertain and how show previous the previous closing stock ?