Will not allow permission to add mileage. It says I don't have access. Can anyone advise?

Welcome to the Community space. I'll help you get through this so you can add mileage option to your QuickBooks Online (QBO) company.

Before we do so, I'd like to share a possible reason why you can't add the option to your company. Please know that in QBO, there are user roles, and that said, you'll have to be the Primary admin of the company to be able to utilize this feature. If you're not the company admin, you can ask your admin to give you access to add the mileage feature. You can also ask them to add this option inside the QBO company instead.

For more information about this, please see this article: User roles and access rights in QuickBooks Online.

Once everything is set inside the company, here's how you can add mileage: Automatically track mileage in QuickBooks Online.

Also, if you got time, I'd recommend checking page to help you add more details to your reports in QBO: Customise reports in QuickBooks Online.

As always, you can post here again if you need further assistance with this or have any additional QuickBooks-related concerns. I'll be more than happy to help you again. Take care, and have a nice day!