Hi..can I add 3 x additional columns to incorporate medical codes, on a sales invoice?

Hello, EnqSA. 

QuickBooks Online (QBO) has its own set of default columns that you can enable and incorporate into your sales invoice. Adding three more columns specific to medical codes isn't an option. With this, I'll provide you with a workaround and encourage you to send feedback or product recommendations to help improve the features and your experience with the program.

Since adding more columns for medical codes on your invoices isn't currently an option, you'll want to include the said information into your item's (product and service) description. You can refer to the screenshot below or to this article for your reference: Add product and service items to QuickBooks Online.

On the other hand, I would encourage you to send suggestions or product recommendations. We'll take them as opportunities to improve the various features of our products. Here's how:

1. Go to the Gear icon.
2. Select Feedback.
3. Type in your recommendation in the Share your feedback field.
4. Click Next.
5. Follow the on-screen instructions to complete the process. 

Additionally, you may want to visit the Sales page to view the status of your sales transactions, open invoices, and paid ones. For the complete guide on how to do this, check out this article: View sales transactions in QuickBooks Online.

Please feel free to comment below if you have other feature concerns or questions about managing invoices and sales transactions in QBO. I'm always ready to help. Take care, EnqSA.