TDSR(Total debt service ratio)=(payment of principal and interest on mortgage+property tax +heating costs+50% of condominium fees+payments on other personal loan)/grss income. TDSR guidelines Currently range ( V; R; o! k# N+ S! O( W! ^) m7 Jfrom 35% to 42% of gross income. $ @: b5 [; C% N+ x5 e% RGDSR(gross debt service ratio)=(payment of principal and interest on mortgage+property taxes+heating costs+50% of condominium fees)/gross income.