Earlier, TDS used to be deducted on the gross amount of the bill (other than rent). But now, CBDT has issued a circular to clarify the issue. Please refer to Circular No. 1, dated 13.01.2014:
"If, as per the terms of the agreement between the payer and the payee, the amount of service tax is to be paid separately and was not included in the fees for professional services or technical services, no TDS is required to be made on the service tax component."
You can refer to the circular to inform your clients in case tax is deducted on the Service Tax part of the invoice.
Thanks & Regards,
Sukhvinder S. Bhatia
So, when entering into an agreement with your vendors, include a clause that Service Tax would be charged separately other than the fees or value agreed.