I need help with invoice numbers

Good morning, @bobbya. I'll assist you with your invoice numbers in QuickBooks Online.

To give you the best answer, I need to know some more information on what you're seeking. Are you wanting to make custom numbers or are you receiving duplication errors when creating the transaction? 

QuickBooks automatically assigns numbers to your sales forms starting with 1001. If you'd rather use your numbering format, you can customize the number to whatever you prefer. I've provided steps below on how you can do this.

How To Set Custom Number on Invoices:

1. Go to the Gear icon, then Account and Settings (or Company Settings).
2. Select Sales.
3. Click anywhere within the Sales form content section to edit.
4. Check the box next to Custom transaction numbers.
5. Press Save and then Done.
6. Open an Invoice, and in the Invoice no. field, enter the custom number or letter sequence you want to use.

**Once you've set up your custom invoice numbering, turn off the Custom transaction numbers feature. This will help prevent accidental changes to your numbering and duplication. Turning this feature off means the Invoice no.  is hidden in your sales form, but still visible for your customers.

Finding duplicated invoices is simple. In just a few clicks, you can see the transactions you made. Here's how:

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

If you like the idea of customizing transactions in your account, here's an article on how to Customize your invoice emails.

The Community has all the answers for you're looking. Let me know if you need anything else. Have a nice day.