Why when I’m creating a new invoice, it says number allready exists? There no number in the box and is normaly computer generated

It's my pleasure to assist you with this, ksbwastemanageme.

QuickBooks Online (QBO) automatically enters the Invoice numbers sequentially. When an invoice number is manually entered, it follows the sequence from the last invoice number used which may already have been used.

To correct this, locate the transaction that uses the same invoice number. Below are the instructions on how to do so:

1. Select Sales from the left menu.
2. Select the No. column to sort it.
3. When the Sales populate, it toggles the numbers in ascending and descending order.
4. Check for duplicates.

Here's an article to learn more about the different ways of finding duplicate invoices in QBO: How to find duplicate invoice and other transactions.

Find out more information about customizing invoices and other sales forms through this article: Customise invoices, estimates, and sales receipts in QBO.

Otherwise, we can try some basic troubleshooting. Have you tried accessing your account via a private browser? Let's check to see if it's a browser issue and then log in to your QuickBooks account. Then, try creating an invoice again.

If it's working fine, go back to your regular browser and clear your browser's cache.

If you want to review the invoices you made, run the Invoice List. Pull this up by going to the Reports menu at the left pane then type Invoice List on the search bar.

To prevent duplicate invoice numbers in the future, we can customize your Accounts and Settings preference.

Here's how:

1. Click the QuickBooks Gear icon.
2. Select Account and Settings.
3. Click the Sales tab.
4. Click the Sales form content section.
5. Uncheck the Custom transaction numbers box.
6. Click Save, then Done.

Be sure to drop me a reply if you have additional questions. I'd be more than happy to help. Stay safe and have a good one.