When I put something into the category of car/van expenses (petrol) it comes up as disallowable expenses why is this

Hello,@richard-crook.

In QuickBooks Self-Employed (QBSE) only travel expenses/costs (fuel, parking, train or bus fares) will be tag as allowable expenses. For more information, you can check out this link: Expenses if you're self-employed.

Also, I consider reading this article for more information about SA103F Categories.

Get back to me if you have any other questions. I'm here to help. Have a good day!