In 35th meeting of the GST Council, It decided to implement E-Invoicing for specific categories of persons. 
As per the government guidelines for e-Invoicing, the e-invoices shall be generated for B2B invoices, using compliant accounting or billing software that supports generating e-invoices in the format prescribed by the government with all the mandatory fields.
The National Informatics Centre launched the first IRP at einvoice1.gst.gov.in.
The e-invoicing was first made applicable on 1st October 2020 for large enterprises. 
The taxpayers must comply with e-invoicing, if annual aggregate turnover exceeds the specified limit in any financial year from 2017-18. Further the aggregate turnover will include the turnover of all GSTINs under a single PAN across India. The specified turnover limit for E-invoicing is given below:-

• • W.e.f. 1st October 2020 = E-invoice If turnover exceeds Rs. 500 cr. 
  • W.e.f. 1st January 2021 = E-invoice If turnover exceeds Rs. 100 cr. 
  • W.e.f. 1st April 2021       = E-invoice If turnover exceeds Rs. 50 cr. 
  • W.e.f. 1st April 2022       = E-invoice If turnover exceeds Rs. 20 cr. 
  • W.e.f. 1st October 2022 = E-invoice If turnover exceeds Rs. 10 cr. 
  • W.e.f. 1st August 2023   = E-invoice If turnover exceeds Rs. 5 cr. 

CBIC vide Notification No. 10/2023–Central Tax dated 10.05.2023, reduced the e-invoicing turnover limit to Rs 5 Crore, to be implemented w.e.f August 1, 2023.
This means that e-Invoice generation will be Mandatory for every taxpayer with an annual aggregate turnover exceeding Rs 5 Crore in any year from 2017-18 onwards to generate e-invoices for B2B supplies w.e.f. August 1, 2023.