eway bill

Yes.

EWB is required to be generated before the commencement of movement of goods. There is no time limit prescribed within which it has to be generated from the date/time of invoice.

Hence, there could be gap (even in number of days) between date/time of invoice and time of generation of EWB.

However, once “Part A” of EWB has been generated, the detail of vehicle has to be filled in Part B within 15 days from the date of filling of “Part A”.

yes, you can issue EWB at the time of commencement of movement of good. 

Invoice date has nothing to do with date of EWB