Service frm mid-month -what will be due date for paying st?

anamika (None ) (28 Points)

08 February 2016  

I am working as individiual consultatant, and  have  been providing service to an IT company since 14th Sep 2015. Invoice date is every month 14th. 

1. For the service period 14th Sep-2015 to 13th Oct-2015, what will be the due date for paying ST? 

Please note that, though the invoice date has been 14th Oct, I have recieved the fees on 21st November. 

Please treat this query as urgent. I have not paid any ST till date. Thrughout my porfessional career I have worked as a salaried person, and  I am completely new to this.