I know a way how to take off one of your vehicles in QuickBooks Self-Employed (QBSE) to help you track your mileage and expenses accordingly, uollaf.

We can make your vehicle inactive so it won't appear in your list of vehicles inside your company file. We can choose the Vehicle no longer in use option to move them to the Inactive section. Let me guide you how:

1. Go to Apps, then select Mileage.
2. Click the ▼ dropdown next to Add trip.
3. Select Manage Vehicles.
4. Choose the vehicle you want to make inactive.
5. Tap Vehicle no longer in use. This moves your vehicle to the Inactive section of your Manage vehicles pane.

The Vehicle no longer in use option will only show if it's a non-primary vehicle. Please see the screenshots for your reference.

 I've also included some articles that will help you in tracking and managing your business miles:

• Manually track mileage 
• Automatically track mileage

Apart from that, I've also got you this helpful article about handling bank transactions inside QBSE: Categorize transactions in QuickBooks Self-Employed.

I've always got your back should you need assistance when doing tasks in QBSE such as adding trips and managing your mileage. Drop your reply anytime and I'll get back to you. Take care always.