One can verify the authenticity or correctness of e-invoice by uploading the signed JSON file or Signed QR Code (string) on the e-invoice portal: einvoice1.gst.gov.in > Search > ‘Verify Signed Invoice’

Alternatively, with the “Verify QR Code” mobile app, which may download from einvoice1.gst.gov.in > Help > Tools > Verify QR Code App.