E invoicing

The taxpayers with annual aggregate turnover of over Rs 500 Crore can voluntarily generate e-invoices starting from 7 January 2020 through APIs. Whereas the taxpayers with the turnover over Rs 100 but less than Rs 500 Crore can join them from 1 February 2020. The electronic invoicing will be mandatorily implemented from 1 April 2020. for taxpayers with turnover over Rs 100 Crore. The aggregate turnover will include the turnover of all GSTINs under a single PAN, across India.

E-invoice presently applicable where GSTIN of the recipient is mandatory - B2B, deemed exports & SEZ supplies. 

B2C, exports are expected to be implemented in phase 2 of implementation. 

Suggest you to go through the FAQ for more clarity (attached!)