Hi there, @Spiceworld. I'm here to share some details about how QuickBooks Self-Employed (QBSE) calculate vehicle expenses.
In QBSE, if an expense is not wholly and exclusively used for business purposes, it will be tagged as a disallowable expense. The program also uses the simplified expense method to calculate the allowable business expense for your car, van, or motorcycle. For more details, check out this link: About car, van, and travel expenses.
To fix your vehicle expenses, make sure to tag these transactions as business type expenses so they will be shown as an allowable expenses. If confirmed that they have been categorised that way, I recommend contacting your accountant to help you claim it and guide you in calculating allowable expenses. If you're not affiliated with one, you can use our Find an Accountant tool to look for one near you.
For reference, please check these articles:
If you have any other concerns about managing your expense transactions in QBSE, please don't hesitate to post again here. I'm always around ready to lend a hand. Have a good one and stay safe.