Challan is a form used for tax payment
Since Vat is under State Government,due dates are different from state to state
Due Date for Vat
In Delhi,Due Date of Challan is 21st of Next Month
Form No is DVAT 20
Example
Month and Due Date
Jan-21 Feb
Feb-21 March
March-21 April
Same due date for CST
CST is also collected by same Vat Department
Hence due date for CST is also same as Vat