税负率=（销项税额—进项税额）/销售收入销售收入=50000/1.17=42735.04销售税额=42735.04*0.17=7264.96如果税负率按3.5%来算的话，需缴纳税额=42735.04*3.5%=1495.73故本月你需认证进项税额为7264.96-1495.73=5769.23