How do I change a mileage rate?

Hello there, @fc_tracy.

Thanks for dropping by here in QuickBooks Community. I'm here to help and guide you on how to change the mileage rate in QuickBooks Online (QBO). 

If you setup the mileage rate on your Product and Services, here's how you can change the rate: 

1. On the left navigation bar, click Sales.
2. Choose Product and Services.
3. Look for the Product and Service name that you want to change the rate, and click Edit.
4. Make necessary changes on the Sales price/rate. 
5. Click Save and close. 

However, if you setup the mileage on billable rate of your vendor's profile, here's how you can update the rate: 

1. On the left navigator bar, click Expense.
2. Choose Vendors. 
3. Double-click the vendor's name, and click Edit.
4. Make necessary changes on the Billing rate (/hr). 
5. Once done, click Save. 

Please let me know how it goes. If you're referring to something else, please leave a comment below. I'll be sure to get back to you.