Dear Bindu,
Tell your client to make travel and accommodation arrangements for you or your trainer. Therefore, the question of payment of TA/DA will not arise. Going further, tell the client to provide a PO on the company letterhead. PO is a legal document under the provisions of Indian Contract Act, 1872.
To avail of services from the service provider or to purchase the material, companies issue a PO to the service provider or a supplier. In your case, you will provide training services, therefore, a description of the type of services may be written clearly on PO. Most companies have standard formats of PO. Additional requirements if any, may be attached as an appendix to the PO.
In PO, the important thing is the charges for your services and payment terms. "Payment Terms" means how many days the company will clear your invoice after receiving it. If you are conducting the training, then it is better to hand over the hard copy of your invoice on the last day of the training. Attach to your invoice, a copy of your PAN card No and TIN if you have registered for the service tax.
When I conduct the training programme on behalf of some training company, I tell them to provide PO to me. I do not bother whether they have taken any PO from their client. That is their lookout.
All the best!
Dinesh Divekar
+91-9900155394