Source doucemnet no. in st3 form

Just now I tried , another row added.

Please see below for  source doc no. 

your STR no_premises code_ST3_MMYYYY.

eg: xxxxx_xxxx_ST3_042012.

Thank You Mr. Sathya.

After reading your reply I tried to add column but was unable to add. But as you said that you added the column just now, so I thought there must be some mistake in form. I downloaded the new form and filled again, this time column added properly and I filed my returns successfully. Thank you for your help.