Hello, How can I fill out the special/custom fields my employer wants me to use when creating an invoice?

You can only use custom fields using a web browser, scooters-solutio.

I appreciate you for sharing this feedback about utilizing custom fields using the app. I suggest submitting your ideas to our product developers. They review submitted feedback for future enhancements and use those suggestions to develop changes for the product. 

Here's how:

1. Select the Gear icon at the top, then Feedback.
2. Enter your comments or product suggestions. Then select Next to submit feedback.

Your valuable feedback goes to our Product Development team to help improve your QuickBooks experience. You can track feature requests through the QuickBooks Online Feature Requests website.

In the meantime, you may continue using custom fields via a browser.

I've also included a detailed resource about working with custom fields in QBO: Create and edit custom fields in QBO Advanced.

Get back to the Community if you have any other additional questions. We're always here to back you up.