It’s great to see you today, pseltsam.

Thanks for joining the QuickBooks Community. You'll have to customize the invoice template so you can manually enter the invoice number.

I’ll walk you through the process:

1. On the Invoice page, click the on the Formatting tab located in the upper left.
   
2. To tailor it, click on the Customize Data Layout icon.
   
3. On the Additional Customization page, go to the Header tab.
   
4. In the Invoice Number section, unmark the boxes for Screen and Print. This will remove the invoice number field.
5. Click on OK.
   

Once done, the default Invoice # field will no longer show on the transaction. However, in the right-hand corner, you’ll see the INVOICE NUMBER field.

You can use that box to manually enter the transaction number. Please know that even if you’ll disable the Invoice # field, QuickBooks will sequentially assign the number for reporting purposes.

For future reference, check out the Use and customize form templates article.

That should do the trick. Let me know about your success following these steps. I’ll be right here if you need further assistance.