I lost "Tracking No." field from my invoice form

Hello there, @ihtemamrentacart.

You'll have to make sure that you add the tracking no. to your invoice. Let me guide you how.

1. Go to the Gear icon.
2. Select the Custom Form Styles.
3. Click New style, then select Invoice.
4. Select the Content, then click the Header.
5. Under the Display section.
6. Tick the box beside the Shipping.
7. Hit Done.

For more details, you can check this article: Customize your invoices, estimates, and sales receipts in QuickBooks Online.

You're most welcome to post another question if you have other questions in mind. Thanks!