HI Caroline,
Thanks for posting in the Community!
The customer will not be notified once you edit or void an invoice not unless you click on Save and send after making changes. Just make sure to click on Save or Save and close. The changes you make is only internal and only for your company.
Here's how:
- Go to the Sales menu.
- Select the Invoice tab.
- Find the appropriate invoice and then open it.
- Make the necessary changes.
- When you're done, click select Save and close or Save.
In addition, here's an article that you can read to learn how to personalize and design your invoices in the program: Customise invoices, quotes, and sales receipts in QuickBooks Online.
Drop by again in the Community of you have further concerns.