Yes, as long as you have the correct permissions to do so, you can update this in your account. See below:
To Enable Custom Invoice Numbers:
- Top right, click your name and select Settings (see below if you do not see the Settings option)
- Click on the System tab.
- Click the Edit Settings button.
- Place a check to the left of Enable Custom Invoice Numbers.
- Click the Save Changes button.
Once you go through Invoicing – Create Invoice to create a new invoice, the bill will be assigned a specific Invoice number. You can then change this to any number (or letter) and click Save to keep that new invoice number set on that specific invoice. With this option, you can now set your own custom invoice numbers for each of your invoices.
Note: If you do not have the correct permissions, you will not be able to get to the Settings to perform these steps. Please contact your System Administrator to have this option turned on for you.