From F.Y 2010-11 for getting the TDS returns validated - PAN details of 100% deductees are required. In case PAN is unavailable then TDs at a higher rate of 20% (30% in case of sec. 194B, 194BB) is required to be deducted.
In the input file there is a column viz. Rate at which TDS deducted, wherein you have to select the the option of Higher rate than the rate in force. After carrying out this exercise for all the deductees whose PAN is unavailable you will be able to validate the file.
Caution: Incase TDS is not deducted at a higher rate as mentioned above, despite not having PAN details of deductees, then you will subsequently receive a notice for making payment of short deduction of tax.