Good day, Shakiel.
I'm joining this thread so I can further assist you with invoicing.
I created and sent an invoice using the QuickBooks Self-Employed Mobile App and the web version. I added the invoice number on the subject line and it both shows on the email.
If this error occurred on the mobile app, please perform the troubleshooting provided by ChristieAnn. Also, you'll want to send the invoice using a browser. Here are the additional steps if the same thing happens:
- Use the incognito window and send the invoice from there.
- Clear cache.
- Update or use another browser.
Additionally, I just want to make sure that you're using QuickBooks Self-Employed. Based on your descriptions, it seems that you're subscribed to QuickBooks Online. If so, here are some of the articles you can check:
Reply again to this thread if you have additional concerns. Stay safe and healthy!
