QuickBooks offers several built-in safeguards to prevent duplicate invoice numbers, tbertram. I'd be happy to explain these features to you.

Before we proceed further, can you specify which section of QuickBooks you're currently working in? Can you also confirm if you're using QuickBooks Online or the Desktop version?

If you're in the Invoices tab under the Sales menu, you can easily sort the list of invoices by transaction number by clicking the NO. header.

This option is also available in QuickBooks Desktop. Here's how:

1. Go to the Customer Center and proceed to the Transactions tab.
2. Proceed to the Transactions tab, then choose Invoices.
3. Click the Num header to organize the invoices based on their assigned transaction numbers.

Please note that QuickBooks will automatically use the next invoice number from the most recent one when creating transactions.

Additionally, QuickBooks will alert you if a previously used invoice number is detected.

If you have the Desktop version, follow these steps on how to enable this feature:

1. Go to the Edit menu and choose Preferences.
2. Click Sales and Customers, then proceed to the Company Preferences tab.
3. Check the box for Warn about duplicate invoice numbers.
4. Click OK.

If you're using QBO, the same feature is enabled by default and there's no need to adjust your company settings.

I’d like to share these articles with you in case you need to remove duplicate transactions in QuickBooks:

• Remove duplicate transactions in QuickBooks Desktop
• Void or delete transactions in QuickBooks Online

Feel free to ask if you have more questions about creating sales transactions or invoicing customers in QuickBooks. We're here to help and will gladly provide assistance whenever you need it.