First learn some concepts & then see how Form E1 & E2 comes into picture
What is sales by transfer of documents of title: provides that a sale or purchase effected by transfer of documents of title to the goods during their movement from one state to another shall be deemed to take place in the cource of interstate trade or commerce.
Explanation 1 provides that the movement of goods commences when goods are delivered to carrier and terminates when delivery is taken from the carrier.
Explanation 2 provides that where the movement of goods commences and terminates in the same state it shall not be deemed to be a movement of goods from one state to another by reason merely of the fact that in the cource of such movement the goods pass through the territory of any other state.
For example if goods are booked from Delhi to Mumbai by Railway, movement of goods will commence as soon as goods are handed over to the Railway booking office at Delhi for transport. The movement will be deemed to continue even if goods reach Mumbai and are lying in possession of railways. The movement will be deemed to have terminated only when the delivery of goods is taken at Mumbai on submission of railway receipt. Thus goods will be deemed to be in movement for sales tax purposes till delivery is taken at destination
The first sales must be an interstate sales. i.e the first sale must be interstate sales in order to claim the exemption
Suppose W in Punjab sends goods in Delhi and raises invoice on X in Bihar, during the movement of goods X sells goods by endorcing documents of title to goods in favour of Y who is a dealer in U.P and Y sells ultimately goods to Z who is a dealer in Delhi by further endorcing the documents of title while the goods are still in transit.Z finally takes delivery of goods in Delhi and the movement of goods comes to an end.
Now in above example W will issue E-I form to X and will get ‘C form’ from X.
X will issue E-II form to Y and will get ‘C form’ from Y.
Y will issue E-II form to Z and will get ‘C form’ from Z