I created a new invoice and it says i hv used the inv no twice but i didnt what should i do?

You encounter that message if there's a duplicate invoice number, Leekiau. I'll help you sort this out.

First, let's ensure there's no invoice with the same number. Here's how:

1. Click Sales.
2. Go to the Invoices tab.
3. Check the invoice numbers.

If there's no duplicate number, you might be experiencing some browser hiccups. Cases like this, we'll be performing some basic troubleshooting steps. Let's start by opening your account through an incognito window. These are the shortcut keys:

• Google Chrome: press Ctrl + Shift + N 
• Mozilla Firefox: press Ctrl + Shift + P
• Safari: press Command + Shift + N

If you're able to successfully save the invoice, go back to the main browser, then clear the cache. We advise our users to clear them now and then to prevent issues like this.

Also, you can use a different web browser. It could be the browser you're using has issues with our program.

Let me include the article on how to create invoices in QuickBooks Online as a future reference.

You can keep us updated after trying these steps. We're just one comment away.