Having the flexibility to customize the display and format of your invoices helps you add a personal touch to your sales forms. QuickBooks Online is all about giving you control over your books. I'll be happy to guide you with this.
Changing the date format for your invoices is a pretty straightforward process.
Click the Gear icon at the top right of the page.
Choose Account and Settings.
Go to the Advanced tab in the left menu.
Scroll down to the Other preferences section.
Click on the pencil icon to edit and use the Date format dropdown to select the one you'd like.