Deductions, if I'm deducting milage, should I be putting fuel and car insurance as expenses?

Thanks for getting back to us, adamhollickdeliv. I can help share some information about deducting mileage in QuickBooks Self-Employed.

Using the simplified method, you're unable to claim vehicle insurance or fuel costs but can claim all other travel expenses in addition to your simplified amount. 
 

As a workaround, you may consider entering a manual transaction like a split transaction as an expense, if however, you need this to be allowable you would need to select the travel category(on the business side of the transaction) as the car vehicle category on a manual entry will push this into the disallowable section.
 

I'm adding these articles you can read to learn more details on how the simplified expenses method calculates the allowable business expense in QBSE:

• About car, van, and travel expenses.
• Simplified Expenses mileage method (with flat rates) versus Actual costs for vehicles.

Tag me in a comment below if I can be of any additional help with handling your mileage deductions. I'll be sure to help you out.