You'll need to enable the Service date option in your invoice, Henry.
 

Let's double-check if the Service date button is enabled in your Invoice settings.
 

Here's how:
 

1. On your Invoice page, tap the Gear icon.
   
   
    
2. Select the Customization tab.
3. Turn on the Service date button.
   
   
   
    

If you’ve already enabled it and still the issue persists, I recommend clearing your app’s data on your device. This will reset the app to its default settings. Stored cache can make the QuickBooks app behave strangely.
 

Here’s how to clear app data:

1. Open your Settings, then tap General.
2. Tap iPhone Storage and find the QuickBooks Online app.
3. Tap Offload App.
    

Feel free to message us if you have further concerns.