Is there a way of automatically notifying a client (eg sms from QB online) that a quote/invoice has been sent?

Thanks for taking the time to reach to us here, hvanzyl.

I have the information you need. In QuickBooks Online, you have the option to automate the invoice reminders. 

Here's how:

1. Go to Settings > Account and Settings.
2. On the left panel, click Sales.
3. Scroll down to the Reminders section and enable the Auto invoice reminders button.
4. Enter the subject line and and email message. You can also stick with the default message. Tip: We recommend you keep "reminder" in the subject.
5. Hit Save and then Done.

I'm also adding this article to see the steps on how to send the invoice reminder manually: Automate invoice reminders in QuickBooks Online.

To check for other guides and articles, please feel free to browse for a topic in our general support page.

If you have any follow-up questions or other concerns about QuickBooks, please let me know by leaving a comment below. Take care and stay safe.

@hvanzyl 

You may need a 3rd party app to send an SMS to mobile numbers.