Welcome to CiteHR! Allow me to congratulate you on opening your "manpower consultancy & done certain recruitment." However, I am sorry to know that you do not know how to raise invoices for your services.
Well, it is very easy. On your letterhead, type the following:
INVOICE
No.
Date:
To:
(Here type the name of the concerned official)
Company Name
Address
Make a table with column heads such as: Sl. no.; Description; Amount. Under Description, give details about the services rendered, reference of their letter for manpower procurement (if necessary attach an annexure giving details); put the amount in the amount column. Then Item two of the Sl. no column will comprise of service tax if applicable; and finally, the net amount.
Hope the above hints would be sufficient to put you on your way.
Warm regards.